Transient two-dimensional IR spectrometer for probing nanosecond temperature-jump kinetics

Chung, Hoi Sung; Khalil, Munira; Smith, Adam W.; Tokmakoff, Andrei

doi:doi:10.1063/1.2743168

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Optical extinction monitor using cw cavity enhanced detection

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We have developed a Fourier transform two-dimensional infrared (2D IR) spectrometer to probe chemical reactions and biophysical processes triggered by a nanosecond temperature jump (T jump). The technical challenges for such a spectrometer involve (1) synchronization of a nanosecond T-jump laser and femtosecond laser system, (2) overcoming the decreased signal-to-noise ratio from low repetition rate data acquisition, and (3) performing an interferometric measurement through a sample with a density and index of refraction that varies with time delay after the T jump. The first challenge was overcome by synchronizing the two lasers to a clock derived from the Ti:sapphire oscillator, leading to timing accuracy of 2 ns for delays up to 50 ms. The data collection time is reduced by using undersampling with the improved signal-to-noise ratio obtained from a balanced detection scheme with a dual stripe array detector. Transient dispersed vibrational echo and 2D IR spectroscopy are applied to N-methylacetamide and ubiquitin, as examples, and the spectral responses by a temperature elevation and by structural changes of the protein are compared. The synchronization of 2D IR spectroscopy with a nanosecond temperature jump without losing its sensitivity at a low repetition rate opens a new applicability of the nonlinear spectroscopy to probe a variety of molecular structure changes induced by a nanosecond perturbation.

Article Outline

INTRODUCTION
EXPERIMENTAL SETUP
1. Generation of the third order signal
2. 2D IR and DVE spectroscopy
3. T -jump laser
4. Control of the time delay between T jump and probe pulses
5. Collection of transient data (balanced detection)
6. Sample preparation
RESULTS AND DISCUSSION
1. Measurement and calculation of the temperature relaxation
2. Transient DVE spectroscopy
3. Balanced detection
4. T -jump 2D IR spectroscopy
SUMMARY AND FUTURE DIRECTIONS

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KEYWORDS and PACS

Keywords

infrared spectrometers, Fourier transform spectrometers, high-speed optical techniques, spectrochemical analysis, remote sensing by laser beam, synchronisation, optical arrays, photodetectors, infrared spectroscopy, proteins

PACS

07.57.Ty

Infrared spectrometers, auxiliary equipment, and techniques
82.80.Dx

Analytical methods involving electronic spectroscopy
42.65.Re

Ultrafast processes; optical pulse generation and pulse compression
42.62.Eh

Metrological applications; optical frequency synthesizers for precision spectroscopy

ARTICLE DATA

Digital Object Identifier

http://dx.doi.org/10.1063/1.2743168

PUBLICATION DATA

ISSN

0034-6748 (print)

1089-7623 (online)

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$abstract.society.value is a Member of CrossRef

American Institute of Physics

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