Cavity ring‐down optical spectrometer for absorption measurements using pulsed laser sources

O’Keefe, Anthony; Deacon, David A. G.

doi:doi:10.1063/1.1139895

Volume/Page
Keyword
DOI
Citation
Advanced

Volume: Page/Article:

Search Content Type

article doi:

Citation:

New densimeter for cryogenic fluids by magnetic levitation of a high‐T_c superconductor

A new magnetic densimeter for cryogenic fluids has been developed by adapting a magnetic levitation of a high‐Tc superconductor. In this instrument, a superconducting material made of Y–Ba–Cu–O is sealed in a hollow glass buoy, and a stable levitation of the buoy is carried out with the Meissner effect of the superconductor simply by placing the buoy in the fluid above a ring‐shaped permanent magnet. The fluid density is obtained from the magnetic force required to levitate the buoy in the fluid...

Longitudinal discharge N₂ laser with automatic preionization using an LC inversion circuit

A four‐segmented longitudinal discharge low pressure N2 laser (337 nm) is reported in which automatic spark preionization and an LC inversion‐charge transfer excitation circuit are employed. Its laser output power was nearly doubled when the techniques developed here were used. The characteristics of the peak laser output powers are interpreted qualitatively, with the electron densities calculated from the observed discharge voltages and currents.

We have developed a technique which allows optical absorption measurements to be made using a pulsed light source and offers a sensitivity significantly greater than that attained using stabilized continuous light sources. The technique is based upon the measurement of the rate of absorption rather than the magnitude of absorption of a light pulse confined within a closed optical cavity. The decay of the light intensity within the cavity is a simple exponential with loss components due to mirror loss, broadband scatter (Rayleigh, Mie), and molecular absorption. Narrowband absorption spectra are recorded by scanning the output of a pulsed laser (which is injected into the optical cavity) through an absorption resonance. We have demonstrated the sensitivity of this technique by measuring several bands in the very weak forbidden b¹Σ_g−X³Σ_g transition in gaseous molecular oxygen. Absorption signals of less than 1 part in 10⁶ can be detected.