Spectroscopy Doppler

Fig. 22. Photofragment Doppler spectroscopy of C3HD4 revealing H-loss, and thus cleavage of the central C—H bond, to be the dominant reaction channel. The allene is the preferentially formed product. (From Deyerl et a .145,149)...

Doppler spectroscopy spect A technique for measuring the speed with which an object is moving toward or away from the observer by measuring the amount that light from the object is shifted to a higher or lower frequency by the Doppler effect. dap-l3r spek tras-ko-pe)... 

Purely Rotational Coherence Effect and Time-Resolved Sub-Doppler Spectroscopy of Large Molecules, P. M. Felker, J. S. Baskin, and A. H. Zewail, J. Chem. Phys. 86,2460 and 2483... 

Dixon, R.N., Nightingale, J., Western, C.M., and Yang, X. (1988). Determination of the pair correlation of the OH rotational states from the 266 nm photolysis of H2O2 using velocity-aligned Doppler spectroscopy, Chem. Phys. Lett. 151, 328-334. 

Xu, Z., Koplitz, B., and Wittig, C. (1987). Kinetic and internal energy distributions via velocity-aligned Doppler spectroscopy The 193 nm photodissociation of II2S and HBr, J. Chem. Phys. 87, 1062-1069. 

Baskin, J.S., Felker, P.M. and Zewail, A.H. (1987). Purely rotational coherence effect and time-resolved sub-Doppler spectroscopy of large molecules. II. Experimental, J. Chem. Phys., 86, 2483-2499. 

V. V. Vlasenko. Studies on photo-sensitivity of unicellular moving micro-algae by method Doppler spectroscopy, Reports of the National Academy of Sciences of Ukraine 11, 172-178 (2004). 

An optical technique involving Doppler spectroscopy can also serve to gain insight into the angular and velocity distributions of reaction products, as reviewed in Ref. [43]. Finally, the Doppler method has been associated with the imaging technique. This is the so-called Doppler-selected time-of-flight technique, which is the most powerful one to obtain information on the three-dimensional (3D) velocity and angular distribution of the reaction products [44-46]. 

J. M. Mestdagh, J. P. Visticot and A. G. Suits, Doppler Spectroscopy, a Powerful Tool for Studying Molecular Collision Dynamics, in The Chemical Dynamics and Kinetics of Small Radicals, edited by K. Liu and A. Wagner, pp. 668-729, World Scientific, Singapore, 1995. 

Precedents for EM distributions of similar width to those depicted in Figure 7 have been generated for other material systems by a measurement technique that is capable of directly resolving the distribution laser-doppler spectroscopy(29). While the present measurement technique provides no information about the frequency function for the distribution, a physical basis does exist for the creation of such a distribution within a powder comprised of nominally identical particles as well as within the two component mixtures. 

PURELY ROTATIONAL COHERENCE AND SUB-DOPPLER SPECTROSCOPY. Guided by the theoretical decay simulations of Fig. 46, the first unambiguous observation of thermally averaged rotational coherence effects was made for excitation and detection of the S, - S00° band of jet-cooled t-stilbene.47 Observed fluorescence decays are shown in Fig. 47 theory and experiment match very well. The recurrences associated with rotational coherence effects in fluorescence have been observed for a number of other species as well. Among these species are t-stilbene-, 2, t-stilbene-argon complexes,48 and t-stilbene-he-lium complexes.71 The recurrences allow the determination of the excited-state rotational constants to a high degree of accuracy. [For example, for t-stilbene we find j(B + C) to be 0.00854 + 0.00004 cm-1.] The indications are that with currently available temporal resolution, rotational coherence effects should be observable in a multitude of species and should allow the accurate determination of such species excited-state rotational constants. 

The probed nascent fragment population traveling with a distribution of velocities will give rise to a Doppler profile about v0. Analysis of this profile can lead to a state-specific P(Etrans) for the photodissociation process [31,44-50], A variation of Doppler spectroscopy can be accomplished by measuring a series of Doppler profiles and changing the delay time between the PUMP and the PROBE steps between each measurement. This technique, known as velocity-aligned Doppler spectroscopy (VADS), is a more direct observation of the speed distribution of the probed molecule along kpr, rather than just a measurement of the velocity components in this direction [51]. As is clear from the above theoretical... 

The resolving power of FM Doppler spectroscopy is demonstrated in the dissociation of ICN at 248 nm. North and Hall [71] were clearly able to resolve the two spin-orbit states of an I atom in the Doppler profile of the CN fragment. As seen in Figure 4, there are two distinct components in both the raw FM signal and the Doppler profile. Further experiments are currently being performed on this system. 

Following the Doppler spectroscopy work of Sivakumar et al. [31], several ion imaging experiments have been done on OCS. As mentioned... 

This chapter is concerned with experimental investigations of the dynamics of the dissociation of polyatomic neutral molecules carried out by the technique of laser Doppler spectroscopy, in bulk and under crossed-beam condition. Photodissociation is a basic process in the interaction of light with molecules, of interest in itself as an elementary molecular process and also with respect to a variety of applications in different fields. The interest has increased considerably in recent years, first, because the experimental investigation of photodissociation is rapidly advancing by the use of the laser, and second, because the laser makes possible to achieve photodissociation, state, and isotope selectively, by new excitation mechanisms. These are, aside from the common one-photon absorption, stepwise... 

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