Laser optoacoustic spectroscopy

V. P. Zharov and V. S. Letokhov, Laser Optoacoustic Spectroscopy, Springer-Vedag, Berlin, 1986. 

L.B. Kreutzer, Laser optoacoustic spectroscopy a new technique of gas analysis. Anal. Chem. 46, 239A (1974)... 

The optoacoustic effect, based on partial non-radiative dissipation of the absorbed light energy, followed by generation of an acoustic wave, was discovered about a hundred years ago. The effect is very weak and, before the advent of lasers, it was applied mainly for spectroscopic investigations of gases. Lasers and improvements in acoustic vibration detection have led to the development of laser optoacoustic spectroscopy (LOAS). Several physical processes are involved in LOAS (1)... 

Zharov VP and Letokhov VS (1986) Laser Optoacoustic Spectroscopy. Springer Series in Optical Sciences, Vol 37. Berlin Springer. 

ROTHBERG L., (1987), Pulsed Laser Optoacoustic Spectroscopy in the Study of Surface Adsorbate Structure and Dynamics, J. Phys. Chem., 91. 

S. E. Braslavsky, R. M. Ellul, R. G. Weiss, H.Al-Ekabi, K. Schaffner. Photoprocesses in Biliverdin Dimethyl Ester in Ethanol Studied by Laser-Induced Optoacoustic Spectroscopy (.LIOAS). Tetrahedron 1983, 39, 1909-1913. 

Photoacoustic or optoacoustic spectroscopy, which detects the absorption of a pulsed laser in a cell by the pressure pulses generated when the light energy is degraded to heat, which is claimed to have sensitivities of 0.4 ppb for nitric oxide and 5 ppb for ethylene, and which can measure the absorption spectra of solids and dusts. ... 

The energy released as heat in the course of the nonradiative decay of P to the ground state and detected as a pressure wave by laser-induced optoacoustic spectroscopy (LIOAS) exhibits positive deviations (i.e., a> 1 cf. Eq. (1)) from the values which were calculated on the basis of the absorption spectrum of Pr alone (Figure 15) [90,115]. This indicates that already within the 15-ns duration of the excitation flash, one or several intermediates must have been formed. These in turn, within the same interval, may again absorb light from an intense laser flash and (at least in part) dissipate heat upon their return to the ground state of the same species (internal conversion) and/or to Pr (photochemical back reaction). The formation of primary photoproducts within the nanosecond flash duration was of course to be expected in view of the much shorter lifetimes of the photochromic fluorescence decay compo-... 

Photoprocesses in biliverdin dimethyl ester in ethanol have been studied by laser-induced optoacoustic spectroscopy." The picosecond kinetics of excited-state relaxation of this ester have also been reported." " Isophorcarubin is a conformationally restricted and highly fluorescent bilirubin." " The phototherapy for neonatal jaundice has stimulated investigations of configurational isomers of bilirubin" and of stereospecific and regioselective photoisomerization of bilirubin." ... 

Braslavsky, S.E., Ellul, R.M., Weiss, R.G., Al-Ekabi, H., and Schaffner, K. (1983) Pytochrome model 7 photoprocessesin biliverdin dimethyl ester in ethanol studied by laser-induced optoacoustic spectroscopy (LIOAS), Tetrahedron, 39, 1909-1913. 

For the spectroscopy of vibrational-rotational transitions in molecules the laser-excited fluorescence is generally not the most sensitive tool, as was discussed at the end of Sect. 1.3.1. Optoacoustic spectroscopy, on the other hand, is based on colli-sional energy transfer and is therefore not applicable to molecular beams, where collisions are rare or even completely absent. For the infrared spectroscopy of molecules in a molecular beam therefore a new detection technique has been developed, which relies on the collision-free conditions in a beam and on the long radiative lifetimes of vibrational-rotational levels in the electronic ground state [84-86]. 

Fig. 1.63 Comparison of overtone spectra of C2H2 around k = 1.5 pm, measured (a) with a Fourier spectrometer and (b) with a color-center laser and intracavity optoacoustic spectroscopy [74]...

The main part of the book presents various applications of lasers in spectroscopy and discusses the different methods that have been developed recently. Chapter 6 starts with Doppler-limited laser absorption spectroscopy with its various high-sensitivity detection techniques such as frequency modulation and intracavity spectroscopy, cavity ring-down techniques, excitation-fluorescence detection, ionization and optogalvanic spectroscopy, optoacoustic and optothermal spectroscopy, or laser-induced fluorescence. A comparison between the different techniques helps to critically judge their merits and limitations. 

During the last 30 years the development of laser technology has opened up new possibilities in analytical spectroscopy, both by improvements in traditional analytical techniques, such as absorption and fluorescence or optoacoustic spectroscopy, and by the introduction of new techniques such as multistep photoionization spectroscopy. thermal lens spectroscopy, and site-selection spectroscopy. 

Laser induced optoacoustic spectroscopy, LIOAS, is a very suitable method to study the radiationless decay processes of excited states. We have applied this method of LIOAS to access the total balance of energy in the intramolecular exciplex systems.[32]... 

Laser Induced Optoacoustic Spectroscopy Laser Magnetic Resonance Laser Spectroscopy Theory Laser Spectroscopy Theory... 

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