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Jan 2003

Volume 74, Issue 1, pp. 1-912

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back to top SPECTROSCOPY, ANALYTICAL CHEMISTRY, AND PHOTOCHEMISTRY

Practical analysis of polymers with depth varying compositions using Fourier transform infrared photoacoustic spectroscopy (plenary)

John F. McClelland, Roger W. Jones, and Siquan Luo

Rev. Sci. Instrum. 74, 285 (2003); http://dx.doi.org/10.1063/1.1516244 (6 pages) | Cited 2 times

Online Publication Date: 16 January 2003

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Fourier transform infrared photoacoustic spectroscopy can be used as a nondestructive method to probe the molecular composition of materials as a function of depth into the sample. This is done by varying the thickness of the surface layer being analyzed, which can be as great as some tens of micrometers, depending on optical and thermal properties. Computational methods are described to process photoacoustic amplitude and phase spectra for both semiquantitative and quantitative depth analyses. These methods are demonstrated on layered and gradient samples. © 2003 American Institute of Physics.
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82.80.Kq Energy-conversion spectro-analytical methods (e.g., photoacoustic, photothermal, and optogalvanic spectroscopic methods)
43.58.Kr Spectrum and frequency analyzers and filters; acoustical and electrical oscillographs; photoacoustic spectrometers; acoustical delay lines and resonators
81.70.Cv Nondestructive testing: ultrasonic testing, photoacoustic testing
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques

Thermal lens temperature scanning for quantitative measurements in transparent materials (invited)

J. H. Rohling, J. R. D. Pereira, A. N. Medina, A. C. Bento, M. L. Baesso, J. A. Sampaio, S. M. Lima, T. Catunda, and L. C. M. Miranda

Rev. Sci. Instrum. 74, 291 (2003); http://dx.doi.org/10.1063/1.1517157 (6 pages) | Cited 2 times

Online Publication Date: 16 January 2003

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In this work the ability of thermal lens spectrometry for different temperature studies in transparent materials is discussed. The method was applied in polymers and optical glasses to measure the thermo-optical properties as a function of the temperature. The focus of the discussion will be on the temperature range where the glass transition occurs. The perspectives of future studies in this area will be discussed. © 2003 American Institute of Physics.
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78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Effect of sensitization by quantum-sized CdS on photoacoustic and photoelectrochemical current spectra of porous TiO2 electrodes

Taro Toyoda, Jun Sato, and Q. Shen

Rev. Sci. Instrum. 74, 297 (2003); http://dx.doi.org/10.1063/1.1515898 (3 pages) | Cited 13 times

Online Publication Date: 16 January 2003

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We report the optical absorption characteristics of highly porous, polycrystalline TiO2 electrodes, on which CdS nanocrystal particles are adsorbed, measured by the photoacoustic (PA) method together with the photoelectrochemical (PEC) current characteristics. The PA spectrum shifts to the lower photon energy region and the intensity below the band-gap energy of TiO2 increases rapidly with an increase in the number of CdS coating layers to 20 and becomes almost constant at more than 20 layers, indicating the possibility of the growth of CdS coated layers. The increase in PEC current intensity and a clear shift of spectra to the lower photon energy region are observed with the increased number of CdS coated layers, indicating the possibility of the transfer of photoexcited electrons of the CdS nanocrystals to the TiO2 conduction band. The PEC current spectrum shifts to the lower photon energy region and the intensity below the band-gap energy of TiO2 increases rapidly with an increase of in the number of CdS coating layers to 20 and decreases with a further increase in the number of layers coated to 40. Thus, nanocrystals of low-band-gap semiconductors are suitable for the sensitization of TiO2 PEC solar cells as well as dye sensitization. © 2003 American Institute of Physics.
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72.40.+w Photoconduction and photovoltaic effects
82.45.Fk Electrodes
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
61.46.-w Structure of nanoscale materials

The effects of eluent’s optothermal parameters on TLS detection in gradient HPLC

J. Kožar Logar and M. Franko

Rev. Sci. Instrum. 74, 300 (2003); http://dx.doi.org/10.1063/1.1515899 (3 pages) | Cited 5 times

Online Publication Date: 16 January 2003

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The effects of changing solvent composition on the limits of detection (LOD) of thermal lens spectroscopy (TLS) detection in gradient elution HPLC have been studied from the perspective of solvent’s thermooptical properties. The refractive index and the temperature dependence of refractive index were measured and are reported for the first time for the methanol-acetone and methanol-ammonium acetate solutions used in this work, and some other methanol based chromatographic eluents. The TLS signal noise during a gradient HPLC protocol is increasing and its value reaches the maximum with a considerable time delay (up to 3 min) compared to the end point of the gradient protocol. The length of the chromatographic column was found to be an important parameter in reduction of signal noise resulting from incomplete solvent mixing. For some carotenoids the LOD values on the order of 50–100 pg/mL can be obtained on a 25 cm column with solvents that yield an increase in TLS enhancement factor up to 1.6 times during the gradient HPLC analysis. © 2002 American Institute of Physics.
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82.80.Bg Chromatography
82.80.Kq Energy-conversion spectro-analytical methods (e.g., photoacoustic, photothermal, and optogalvanic spectroscopic methods)

Buffer-gas pressure influence on multiphoton absorption in SF6–N2 mixtures

D. D. Markushev, M. Terzić, and J. Jovanović-Kurepa

Rev. Sci. Instrum. 74, 303 (2003); http://dx.doi.org/10.1063/1.1515900 (3 pages) | Cited 3 times

Online Publication Date: 16 January 2003

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In this article the results of pulsed IR photoacoustic spectroscopy measurements of multiphoton absorption and relaxation processes in SF6–N2 mixtures are presented. The total average number of absorbed photons per one absorbing molecule (basic physical quantity which characterized multiphoton processes) during the laser pulse 〈n〉total is used and analyzed with a generalized coupled two-level model. This type of analysis is based on buffer-gas pressure (pbuff) functional behavior of 〈n〉total and calculation of its partial values depending on collisions, 〈n〉coll, and laser fluence, 〈n〉Φ, influence. Using different methods of photoacoustic spectroscopy, collisionaly induced rotational and vibrational to translational relaxation process parameters (τrot and τV-T, respectively) are quantitatively obtained and used to determine partial values of 〈n〉coll, 〈n〉rot, and 〈n〉V-T. It will be shown that a method based on ∂〈n〉total/∂p functional dependence on pbuff and laser fluence Φ can be used to confirm or predict the existence of some processes during the laser pulse, such as dissociation or strong vibrational to vibrational energy transfer, which can contribute to the total amount of energy absorbed into the investigated sample. This could allow one to apply this method and control laser field–molecule interaction in different gas mixtures, and help one to understand multiphoton absorption processes in detail. © 2003 American Institute of Physics.
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32.80.Wr Other multiphoton processes
33.80.Gj Diffuse spectra; predissociation, photodissociation
34.50.Ez Rotational and vibrational energy transfer

Determination of physical parameters of conducting polymers by photothermal spectroscopies

J. E. de Albuquerque, W. L. B. Melo, and R. M. Faria

Rev. Sci. Instrum. 74, 306 (2003); http://dx.doi.org/10.1063/1.1515901 (3 pages) | Cited 19 times

Online Publication Date: 16 January 2003

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Photothermal spectroscopies, photopyroelectric and photoacoustic, were used to obtain physical parameters of polyaniline–emeraldine base (PANI-EB) and poly(o-methoxyaniline)–emeraldine base (POMA-EB), such as thermic parameters like thermal diffusivity, thermal conductivity, and specific heat. These studies were done for PANI-EB and POMA-EB films in the 400<λ<900 nm wavelength range. The photopyroelectric intensity Vn(f ) and the phase Fn(f ) (f being the chopping frequency) for a given λ of the saturation part of the PPES spectrum signal were independently measured, as well as the intensity Vn(λ) and its phase Fn(λ). Equations of both the intensity and the phase of the PPES signal, taking into account the thermal and the optical characteristics of the PANI and POMA films and the pyroelectric detector, were used to fit the experimental results. It was observed that, in contrast with the strong doping dependence of the electrical conductivity, the thermal parameters of PANI films remained practically unchanged under doping. This apparent discrepancy is explained by the granular metal model of doped PANI. © 2003 American Institute of Physics.
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78.66.Qn Polymers; organic compounds
07.60.Rd Visible and ultraviolet spectrometers
07.20.-n Thermal instruments and apparatus
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects

Photoacoustic spectral studies on lanthanide amino acid complexes

Yue-tao Yang, Gui-wen Zhao, and Shu-yi Zhang

Rev. Sci. Instrum. 74, 309 (2003); http://dx.doi.org/10.1063/1.1515902 (3 pages) | Cited 1 time

Online Publication Date: 16 January 2003

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Several kinds of lanthanide complexes with glycine, alanine, phenylalanine, and tryptophan were synthesized and their photoacoustic (PA) spectra were measured. For the complexes of weakly fluorescent lanthanide ions with amino acids, the PA spectra reflect the influences of the ligands on the energy levels of lanthanide ions, whereas for the complexes of fluorescent lanthanide ions with amino acids, the PA spectra can be used to study the energy transfer from aromatic amino acids to lanthanide ions. At last, separating the overlapping peaks of lanthanide complex with tryptophan using the PA phase resolved method is introduced. © 2003 American Institute of Physics.
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78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects

Nonradiative processes in transition ions in crystals

M. Grinberg, A. Śliwiński, and A. Sikorska

Rev. Sci. Instrum. 74, 312 (2003); http://dx.doi.org/10.1063/1.1515903 (4 pages) | Cited 2 times

Online Publication Date: 16 January 2003

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We present a model describing a photoacoustic signal in the presence of spatial energy migration from the luminescence center to the surface. The model has been used for describing the relation between photoacoustic and absorption spectra in the YAG:Cr3+ crystal. Considering the frequency dependence of photoacoustic spectra signals and absorption under 348 and 605 nm excitation, we have estimated the radius of the excitation energy diffusion length. © 2003 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects

Acoustic mode suppression in an off-axially coupled resonant cell for laser photoacoustic spectroscopy

K. Nukihara, I. Izuhara, and N. Sokabe

Rev. Sci. Instrum. 74, 316 (2003); http://dx.doi.org/10.1063/1.1515905 (3 pages) | Cited 1 time

Online Publication Date: 16 January 2003

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We report a resonant photoacoustic cell of off-axis coupling type for laser photoacoustic spectroscopy of molecular species at low pressures. Using a waveguide CO2 laser operating on a 9 μm R (10) line and 4% C2H4/N2 standard gas, the time development of the photoacoustic signal from cylindrical resonant horns of different diameters is studied. Fast Fourier transform analysis of the observed photoacoustic signal revealed that (a) the resonant frequency depends strongly on pressure under low pressures, (b) the quality factor increases with pressure as well as with horn radius, (c) the number of excited modes and their relative intensities depend strongly on pressure as well as on horn radius, (d) an increase in horn radius results in multimode excitation and in interference of the modes, and (e) the mode interference tends to spoil the quality factor. An off-axially coupled resonant horn of medium volume is demonstrated to operate essentially on the fundamental axial mode with the quality factor being improved by a factor of 1.5. © 2003 American Institute of Physics.
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82.80.Kq Energy-conversion spectro-analytical methods (e.g., photoacoustic, photothermal, and optogalvanic spectroscopic methods)
43.58.Kr Spectrum and frequency analyzers and filters; acoustical and electrical oscillographs; photoacoustic spectrometers; acoustical delay lines and resonators
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect

Energy and volume changes induced by photoinitiated proton releasing reaction with apomyoglobin

Jungkwon Choi and Masahide Terazima

Rev. Sci. Instrum. 74, 319 (2003); http://dx.doi.org/10.1063/1.1515906 (3 pages) | Cited 4 times

Online Publication Date: 16 January 2003

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The photodissociation reaction of o-nitrobenzaldehyde (NBA) aqueous solution and of the NBA solution with a protein, apomyoglobin (ApoMb), were studied by the time-resolved transient grating (TG) technique. The amount of released thermal energy and the volume change accompanied with this reaction were determined by the TG and photoacoustic method. Without the protein, the photoproduct of NBA releases a proton in the solution (pH jump reaction). The time profile of the grating signal of NBA and ApoMb shows two diffusing species with diffusion coefficients of 1.39±0.15 and 0.14±0.02×10−9 m2 s−1, respectively. From the diffusion coefficients, we suggest that the photoproduct of NBA induces a molecular recombination reaction between ApoMb and another small molecule or ion in the solution. © 2003 American Institute of Physics.
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87.15.M- Spectra of biomolecules
82.50.Hp Processes caused by visible and UV light
87.14.E- Proteins
87.15.Vv Diffusion

Photoacoustic observation of multiphoton absorption and relaxation parameters in gas mixtures

Mira Terzić, Dragan D. Markushev, and Jelena Jovanović-Kurepa

Rev. Sci. Instrum. 74, 322 (2003); http://dx.doi.org/10.1063/1.1517158 (3 pages) | Cited 2 times

Online Publication Date: 16 January 2003

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A method is described that allows simultaneous photoacoustic measurements of multiphoton absorption and relaxation parameters in gas mixtures. The σe method to determine rotational relaxation parameters was developed. Various approaches for evaluating differential cross sections are discussed. © 2003 American Institute of Physics.
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07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment
33.80.Wz Other multiphoton processes
43.58.Kr Spectrum and frequency analyzers and filters; acoustical and electrical oscillographs; photoacoustic spectrometers; acoustical delay lines and resonators
34.50.Ez Rotational and vibrational energy transfer

Study of cross-linking process in grafted polyethylene and ethylene based copolymer using a phase resolved photoacoustic method

D. T. Dias, A. N. Medina, M. L. Baesso, A. C. Bento, M. F. Porto, E. C. Muniz, and A. F. Rubira

Rev. Sci. Instrum. 74, 325 (2003); http://dx.doi.org/10.1063/1.1517159 (3 pages) | Cited 1 time

Online Publication Date: 16 January 2003

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In this work, the phase resolved photoacoustic method has been employed to monitor water saturated vapor cross linking in both copolymer and grafted polyethylene. The overtone bands and stretching frequencies combinations of the –Si–OH, = CH2, –CH3, and –CH2–CH3 were monitored and analyzed accordingly to a 32 factorial design with nine samples. The results showed that the cross-linking processes were more efficient when the samples were prepared at 80 °C with the catalyst in the concentration range between 3% and 5% for grafted PE, while 70 °C was the best temperature to obtain copolymer. © 2003 American Institute of Physics.
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82.80.Kq Energy-conversion spectro-analytical methods (e.g., photoacoustic, photothermal, and optogalvanic spectroscopic methods)

Photoacoustic study of PET films and fibers dyed in supercritical CO2 reactor

L. Olenka, E. S. Nogueiran, A. N. Medina, M. L. Baesso, A. C. Bento, E. C. Muniz, and A. F. Rubira

Rev. Sci. Instrum. 74, 328 (2003); http://dx.doi.org/10.1063/1.1517160 (3 pages) | Cited 2 times

Online Publication Date: 16 January 2003

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Photoacoustic (PA) spectroscopy was applied to study the dyeing process in poly(ethylene terephthalate) films and fibers when supercritical (SC) pressure of CO2 is used. The samples were prepared according to a factorial design having four variables in two levels. They were dyed in red or blue. Following the PA intensity as a variable of response, it was applied an algorithm to take into account the effects of the dyeing variable. The results show that treatment and time were the more influent for blue dyed films and fibers. In contrast, time and temperature were more effective for red films. Depth penetration of the red dye shows saturation near 60 μm with a characteristic time of 30 min. Overall, the results presented CO2 pressure as the less effective variable and the SC–CO2 dyeing method being more effective if compared to conventional bath. © 2003 American Institute of Physics.
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82.80.Kq Energy-conversion spectro-analytical methods (e.g., photoacoustic, photothermal, and optogalvanic spectroscopic methods)
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials

Quantitative analysis of corroded copper patina by step scan and rapid scan photoacoustic Fourier transform infrared spectroscopy

Werner Faubel, Stefan Heissler, and Richard A. Palmer

Rev. Sci. Instrum. 74, 331 (2003); http://dx.doi.org/10.1063/1.1517740 (3 pages) | Cited 1 time

Online Publication Date: 16 January 2003

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Atmospheric corrosion enhanced by increasing air pollution causes increasing damage at valuable metallic monuments worthy of protection, e.g., the roof of the Stockholm City Hall. To explore the potential use of Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) in quantitative corrosion product analysis, the determination of the chemical composition of copper patina samples formed under atmospheric conditions was studied. As an experimental technique, we used a FTIR spectrometer in combination with sample-gas-microphone PAS using helium as the transfer gas at room temperature. The main components of the different samples—brochantite Cu4SO4(OH)6 and antlerite Cu3SO4(OH)4—were identified by their characteristic vibrational absorption bands. A quantitative analysis of these two components has been performed with rapid- and step-scan FTIR/PAS by using artificially corroded copper samples with differing ratios of composition. From these data, calibration curves were obtained allowing a nondestructive determination of the brochantite/antlerite ratio for quality control within an accuracy of about 10%. © 2003 American Institute of Physics.
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82.80.Kq Energy-conversion spectro-analytical methods (e.g., photoacoustic, photothermal, and optogalvanic spectroscopic methods)
82.80.Gk Analytical methods involving vibrational spectroscopy
81.70.Cv Nondestructive testing: ultrasonic testing, photoacoustic testing
43.58.Kr Spectrum and frequency analyzers and filters; acoustical and electrical oscillographs; photoacoustic spectrometers; acoustical delay lines and resonators
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques

Investigation of adsorption by thermal lensing

M. A. Proskurnin, M. Yu. Kononets, S. N. Bendrysheva, E. V. Proskurnina, D. A. Nedosekin, and A. D. Khrycheva

Rev. Sci. Instrum. 74, 334 (2003); http://dx.doi.org/10.1063/1.1517741 (3 pages)

Online Publication Date: 16 January 2003

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Thermal lensing was used for the characterization of adsorption on laboratory glassware at a nanogram concentration level in solution. Sorption kinetics was studied, the sorption capacity of the glass for test substances was characterized, which was found to be several ng cm−2. Factors affecting adsorption were discussed. A procedure for handling laboratory glassware for eliminating sorption effects in determining nanogram amounts of iron in aqueous solutions was developed. © 2003 American Institute of Physics.
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68.43.Mn Adsorption kinetics
82.80.-d Chemical analysis and related physical methods of analysis

Effect of voltage treatment applied on photoacoustic and photoelectrochemical current spectra in final preparation processes of porous TiO2 electrodes

Taro Toyoda and Masashi Hayashi

Rev. Sci. Instrum. 74, 337 (2003); http://dx.doi.org/10.1063/1.1518552 (3 pages) | Cited 1 time

Online Publication Date: 16 January 2003

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We report the effect of different voltages in a concentrated KCl electrolyte applied to highly porous, polycrystalline TiO2 films during their final preparation processes on photoacoustic (PA) and photoelectrochemical (PEC) current spectra. Below the band-gap energy region, the PA signal intensities of the TiO2 films with different voltage treatment applied are higher than those without treatment and they increase with an increase of applied voltage. These experimental results suggest an innerband transition from an increase in carrier concentration due to the formation of donor levels by partially reduced Ti ions (Ti4+→Ti3+) by the voltage treatment. The PEC current spectra for applied voltage treatment over −1.5 V show two peaks above the band-gap energy region whose intensities increase rapidly above applied voltage of −1.5 V (eight times larger for voltage of −3.5 V than those without treatment), which is similar to that of the PA intensity at a photon energy of 2.0 eV. The modulation frequency dependence of the PEC current intensity at the peak position shows different characteristics depending on the voltage treatment applied, indicating the difference in PEC current response due to the formation of donor levels by the treatment. © 2003 American Institute of Physics.
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82.45.Fk Electrodes
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
71.55.Ht Other nonmetals
78.66.Li Other semiconductors

Deep level photothermal spectroscopy for characterizing Ni impurities in Si by a temperature dependent piezoelectric photothermal signal

S. Sato, A. Memon, A. Fukuyama, S. Tanaka, and T. Ikari

Rev. Sci. Instrum. 74, 340 (2003); http://dx.doi.org/10.1063/1.1519673 (3 pages) | Cited 4 times

Online Publication Date: 16 January 2003

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The temperature variation of the piezoelectric photothermal (PPT) signal intensity of n-type Ni-doped Si was measured from 100 to 300 K. We observed one distinctive peak at 150 K in Ni-doped sample. Since no intense peak could be observed for the controlled sample, we consider this 150 K peak is due to Ni impurity. The activation energy, electron capture cross section, photoionization cross section and concentrations for Ni-deep level are obtained by fitting the observed curve to that from the theoretical analysis based on a rate equation for electrons. The best-fitted parameters are well agreed with that obtained by usual deep level transient spectroscopy measurements and isothermal capacitance transient spectroscopy. Additionally, photoionization cross section of Ni-deep level in Si can be obtained by this method. Since no electrodes are necessary in this experimental technique, the PPT measurement for studying the deep level in semiconductor is very useful. © 2003 American Institute of Physics.
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71.55.Cn Elemental semiconductors
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
77.65.-j Piezoelectricity and electromechanical effects

Investigation of Belousov–Zhabotinsky reaction kinetics using thermal lens spectrometry

M. A. Proskurnin, D. A. Nedosekin, and V. V. Kuznetsova

Rev. Sci. Instrum. 74, 343 (2003); http://dx.doi.org/10.1063/1.1519674 (3 pages) | Cited 1 time

Online Publication Date: 16 January 2003

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Thermal lensing is proposed for monitoring unstirred Belousov–Zhabotinsky reaction with a mixture of free Fe(II) and its chelate with 1,10-phenanthroline as a catalyst and a photometric indicator of the reaction process. The optimum initial concentrations of components for stable oscillations in system are found. The sensitivity and reproducibility of thermal lensing was compared to spectrophotometry and potentiometry by the model determination of bromide ions by its inhibition effect on the reaction kinetics. © 2003 American Institute of Physics.
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82.40.Bj Oscillations, chaos, and bifurcations
82.80.Kq Energy-conversion spectro-analytical methods (e.g., photoacoustic, photothermal, and optogalvanic spectroscopic methods)
82.30.Vy Homogeneous catalysis in solution, polymers and zeolites

Near-surface depth-resolved midinfrared emission spectroscopy

I. Notingher, R. E. Imhof, P. Xiao, and F. C. Pascut

Rev. Sci. Instrum. 74, 346 (2003); http://dx.doi.org/10.1063/1.1519675 (3 pages) | Cited 1 time

Online Publication Date: 16 January 2003

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We report the development of a practical instrument that enables depth-resolved midinfrared spectra to be measured in a noncontacting, nondestructive way on samples of arbitrary shape and size and without any prior preparation of the surface. The technique used, thermal emission decay Fourier transform infrared (TED-FTIR) spectroscopy combines time-domain optothermal radiometry with step-scanning FTIR spectroscopy. The instrument uses purpose-designed optics and software to measure optothermal transients at a predetermined number of interferometer path differences, from which depth-resolved spectra in the range 700–1800 cm−1 with a resolution of 12 cm−1 can be calculated. The depth range is limited by the optical and thermal properties of the sample, being ∼10 μm for common organic materials. © 2003 American Institute of Physics.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.60.Dq Photometers, radiometers, and colorimeters
07.60.Ly Interferometers

Two-photon photothermal deflection spectroscopy of atomic sodium (abstract)

Z. Al-Ahmed, Y. J. Li, and R. Gupta

Rev. Sci. Instrum. 74, 349 (2003); http://dx.doi.org/10.1063/1.1521528 (1 page)

Online Publication Date: 16 January 2003

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Two-photon photothermal spectroscopy (with nonresonant intermediate state) is a very useful technique, because many atomic and molecular species that are usually optically inaccessible by single-photon excitation can be made accessible by two-photon excitation. Some examples of atomic species are H and O. As a first step, we are investigating photothermal signals generated in sodium vapor produced by two-photon excitation of the 52S1/2 state at 602.23 nm. Sodium vapor is contained in a glass absorption cell and N2 buffer gas at 0.66 amagat pressure is used to collisionally transfer the optical energy from Na to the rotational-translation (thermal) energy of N2 gas. A pulsed dye laser operating at 602.23 nm provides the pump beam. The absorption cell is heated in an oven to obtain about 5×10−4 Torr of Na vapor pressure. Photothermal deflection of a He–Ne laser probe beam is observed. Results of these experiments will be discussed. © 2003 American Institute of Physics.
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07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment
32.80.Wr Other multiphoton processes
34.50.Ez Rotational and vibrational energy transfer

Photothermal beam deflection spectroscopy using solid deflection media (abstract)

A. M. Gillikin and R. A. Palmer

Rev. Sci. Instrum. 74, 350 (2003); http://dx.doi.org/10.1063/1.1521529 (1 page)

Online Publication Date: 16 January 2003

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Photothermal beam deflection (PTBD) is a useful tool for measuring absorbance spectra, particularly of nontransparent and poorly reflective samples. Unfortunately, the optical alignment for such measurements is often time consuming and difficult to reproduce. The desire for a permanently aligned and robust PTBD probe accessory is the driving force behind the research reported here. The use of a solid deflection medium is the key to developing such an accessory. The source of incident radiation for our PTBD accessory is a Fourier transform infrared spectrometer. The spectrometer allows us to combine infrared spectral information, and thus chemical characterization, with the localized detection capability of the PTBD technique. Various infrared transparent solids, including ZnSe and KBr, have been used as deflection media, and the resultant spectra have been compared to experimental data collected with a more traditional liquid deflection technique. The transparent solid deflection media possess reasonable values of dn/dT and provide broad, unobstructed spectral windows in the infrared region, in contrast to their liquid counterparts. The solid deflection media also provide a rigid platform on which optical devices can be mounted, creating a fixed alignment PTBD accessory with a potential for significant miniaturization. To measure a spectrum, the sample need only make good thermal contact with the inert solid deflection medium at the position of incident IR radiation. This type of device has significant potential for in-field measurements, including, ultimately, microscopic in vitro and in vivo spectrochemical analysis. Here, we present data gathered using solid deflection media for PTBD spectroscopy, and evaluate the performance of each solid and its potential for future use. © 2003 American Institute of Physics.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.20.-n Thermal instruments and apparatus
82.80.Kq Energy-conversion spectro-analytical methods (e.g., photoacoustic, photothermal, and optogalvanic spectroscopic methods)

Measurement of absolute OH concentration in a flame by photothermal deflection spectroscopy (abstract)

Y. J. Li and R. Gupta

Rev. Sci. Instrum. 74, 351 (2003); http://dx.doi.org/10.1063/1.1521533 (1 page)

Online Publication Date: 16 January 2003

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Combustion diagnostics is an important field of research. Efforts are underway in various laboratories to develop a noninvasive technique that can yield absolute concentrations (that is, without the need for calibration against a standard sample) of minority combustion species with high temporal and spatial resolution. Fluorescence techniques are plagued by the problem of quenching collisions. On the other hand, photothermal technique relies on quenching collisions to transfer optical energy to the thermal (rotational–translational) modes of the molecules. Therefore, photothermal deflection spectroscopy (PTDS) is ideally suited for a high-quenching-rate environment, such as combustion. If the quenching rates are much faster than radiative rates, as they generally are in a combustion environment, PTDS offers an opportunity to measure absolute concentration. Temporal resolution is achieved by using pulsed laser excitation and spatial resolution is achieved by crossing the pump and probe beams at a relatively large angle. Our experiments have been conducted in a methane–oxygen flame. OH molecules were excited on the Q1 (8) rotational line at 309.24 nm by radiation from a frequency-doubled pulsed dye laser. Deflection of a He–Ne laser probe beam caused by the photothermal effect was observed. Various effects, which are important in the analysis of the signal for absolute concentration measurement, for example, OH absorption and laser spectral profiles, optical saturation, and spatial profile of the pump laser are thoroughly investigated and will be discussed. © 2003 American Institute of Physics.
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82.80.Kq Energy-conversion spectro-analytical methods (e.g., photoacoustic, photothermal, and optogalvanic spectroscopic methods)
82.33.Vx Reactions in flames, combustion, and explosions
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency

Highly sensitive detection of molecules at the liquid/liquid interface using total internal reflection–optical beam deflection based on photothermal spectroscopy

Masanori Fujinami, Hiromi Murakawa, and Tsuguo Sawada

Rev. Sci. Instrum. 74, 352 (2003); http://dx.doi.org/10.1063/1.1524042 (3 pages) | Cited 1 time

Online Publication Date: 16 January 2003

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In this study, a highly sensitive and versatile method based on photothermal spectroscopy has been developed to monitor the molecular density at a liquid/liquid interface. The excitation under the total internal reflection (TIR) condition results in a formation of a thin thermal lens elongated along the interface. In order to measure the thermal lens effects effectively and to reduce the background, the probe beam is irradiated parallel to the interface and its deflection is detected, which is called an TIR-optical beam deflection (TIR-OBD). As a result, the detection limit in TIR-OBD is about 2 orders lower than that of TIR-thermal lens spectroscopy, in which the irradiation of the probe beam is perpendicular to the interface. © 2003 American Institute of Physics.
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68.05.Cf Liquid-liquid interface structure: measurements and simulations
07.60.Dq Photometers, radiometers, and colorimeters

Photoacoustic spectroscopy applied to the study of clay soils

D. R. dos Santos, R. Toledo, M. S. O. Massunaga, J. G. Carrió, L. T. Auler, E. C. da Silva, A. Garcia-Quiroz, and H. Vargas

Rev. Sci. Instrum. 74, 355 (2003); http://dx.doi.org/10.1063/1.1518553 (3 pages) | Cited 1 time

Online Publication Date: 16 January 2003

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The optical absorption spectra and mineralogical composition of soil samples were characterized using photoacoustic spectroscopy and x-ray diffraction. The photoacoustic spectra observed showed transition bands associated with Fe3+ ions in octahedral or tetrahedral symmetry. From the phase behavior, both the nonradiative relaxation time τ and the characteristic thermal diffusion time τβ were determined. The x-ray diffraction analysis showed that kaolinite is a major crystalline phase (86 wt %) followed by minor quantities of anatase, gibbsite, and quartz. Rietveld refinements showed that the Fe3+ cations partially substitute for Al3+ cations in octahedral sites of the kaolinite structure. © 2003 American Institute of Physics.
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91.60.Lj Acoustic properties
91.60.Mk Optical properties
43.58.Kr Spectrum and frequency analyzers and filters; acoustical and electrical oscillographs; photoacoustic spectrometers; acoustical delay lines and resonators
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
91.60.Ki Thermal properties
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