Optoacoustic method

This temperature rise can be detected directly (laser calorimetry and optical calorimetry), or indirectly by measuring the change in either the refractive index (thermal lensing, beam deflection or refraction and thermal grating) or the volume (photo- or optoacoustic methods). This review will focus primarily on photoacoustic methods because they have been the most widely used to obtain thermodynamic and kinetic information about reactive intermediates. Other calorimetric methods are discussed in more detail in a recent review.7... 

Relaxation of the states of I and Br in collisions with H2 has been studied by optoacoustic spectroscopy and by i.r. emission techniques, respectively. The optoacoustic method allows determination of whether translational energy is absorbed or released in the collision process, and with H 2 it is found that absorption occurs, i.e. there is net translational cooling. The formation... 

Another set of analytical techniques (optocal-orimetric methods) is based on indirect measurement of the energy absorbed by the sample. Absorbed energy is transformed into kinetic energy of the sample particles followed by an increase in the local temperature of the sample. The resultant changes in pressure and refractive index can be measured by optoacoustic methods or by laser scattering techniques. 

In order to qualitatively and quantitatively evaluate the various deactivation channels of the electronically excited bilatriene chromophore in Pr, the photophysical and photochemical parameters of this chromophore were determined by stationary fluorescence [76] and time-resolved spectroscopic methods (for in-house developments and first applications of fluorescence and optoacoustics see [77-80] and [81,82], respectively) [2,9,10,83,84], Furthermore, a time-resolved fluorescence study has been carried out also with the selectively excited tryptophane residues of Pt and Pfr. The results are discussed in Sections II.A-C and III.A. Unless specified otherwise, the experiments were performed in vitro with 124-kDa phytochrome isolated from etiolated oat seedlings (Avena sativa L ), and the measurements were carried out with ethylene glycol-containing phosphate buffer solutions at 3s 275 K. 

The theory of rotation effects on prolate luminescent molecules in solution and its experimental verification have been developed and compared. Generalized diffusion equations for the rotational motion of an asymmetric rigid motor have been used to given an expression for steady-state fluorescence depolarization. " The radiationless transition from the first excited singlet state of Eosin has been measured by optoacoustic relaxation, and the absolute fluorescence quantum yields of organic dyes in poly(vinyl alcohol) have also been measured by the photoacoustic method. The accuracy of the method has been discussed in the latter paper. Actinometry in flash photolysis experiments has been assisted by new measurements on the extinction coefficient of triplet benzophenone. Matrix-isolation fluorescence spectrometry has been used to detect polycyclic aromatic hydrocarbons from gas chromatography. ... 

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. 

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]... 

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