Distributions rotational

An elegant modification ° of the beam apparatus has been the utilization of laser-induced fluorescence as a detection method. In addition to 

Assignment of relative vibrational distributions from emission spectra of polyatomic sources involves several approximations. Each observed band is converted to a relative intensity in order to obtain the relative vibrational distribution that is appropriate to the observed spectrum. The emission from a given vibrational mode, /, is assumed to be produced by At = — 1 transitions from many v levels thus, the observed intensity from the given mode is 

In some instances several modes may contribute to a given observed band and then the sum must be over all of the contributing modes. The are 

The energy content of a given band is related to populations, Ei = N vh(ve, and the experimental energy contents can be used to assign relative values of Ny to the various modes. The relative populations are claimedto be accurate to 5-10% for the polyatomic molecules that have been investigated. 

The chemical laser technique resembles chemiluminescence, but stimulated, rather than spontaneous emission, is observed. One advantage, relative to the chemiluminescence technique, is that the vibrational population for the r = 0 level can be measured. However, unlike the chemiluminescence experiments most laser experiments are done in the 10-100 torr pressure range hence, the initial rotational populations are not measured and in fact rotational equilibration with the bath gas is assumed in obtaining relative vibrational populations. The chemical laser techniques have been recently reviewed, and, further details are not given here. 

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Spectroscopic detemiination of the HE rotational distribution is another story. In both the chemical laser and infrared chemiluminescence experiments, rotational relaxation due to collisions is faster or at least comparable to the time scale of the measurements, so that accurate detemiination of the nascent rotational distribution was not feasible. However, Nesbitt [40, 41] has recently carried out direct infrared absorption experiments on the HE product under single-collision conditions, thereby obtaining a fiill vibration-rotation distribution for the nascent products. 

In Figure 1, we see that there are relative shifts of the peak of the rotational distribution toward the left from f = 12 to / = 8 in the presence of the geometiic phase. Thus, for the D + Ha (v = 1, DH (v, f) - - H reaction with the same total energy 1.8 eV, we find qualitatively the same effect as found quantum mechanically. Kuppermann and Wu [46] showed that the peak of the rotational state distribution moves toward the left in the presence of a geometric phase for the process D + H2 (v = 1, J = 1) DH (v = 1,/)- -H. It is important to note the effect of the position of the conical intersection (0o) on the rotational distribution for the D + H2 reaction. Although the absolute position of the peak (from / = 10 to / = 8) obtained from the quantum mechanical calculation is different from our results, it is worthwhile to see that the peak... 

By contrast, the dissociation channel leading to H + HCO (the radical channel) has no barrier and a dissociation threshold [49] of 30,328.5 cm. In 1993, van Zee et al. [50] found that excitation above this threshold led to CO rotational distributions that were bimodal. In addihon to the high-/ CO... 

The Franck-Condon model, which decomposes the initial quasistable state of the wave function in terms of free-rotor states and gives the product rotational distribution if no torques are present, was apphed to Ne CI2 and He CI2 and correctly predicted the low / behavior of the distribution, as well as the invariance of the distributions in the Av = 1 and —2 channels [99, 100]. 

Gray and Wozny [101, 102] later disclosed the role of quantum interference in the vibrational predissociation of He Cl2(B, v, n = 0) and Ne Cl2(B, v, = 0) using three-dimensional wave packet calculations. Their results revealed that the high / tail for the VP product distribution of Ne Cl2(B, v ) was consistent with the final-state interactions during predissociation of the complex, while the node at in the He Cl2(B, v )Av = — 1 rotational distribution could only be accounted for through interference effects. They also implemented this model in calculations of the VP from the T-shaped He I C1(B, v = 3, n = 0) intermolecular level forming He+ I C1(B, v = 2) products [101]. The calculated I C1(B, v = 2,/) product state distribution remarkably resembles the distribution obtained by our group, open circles in Fig. 12(b). 

Observed angular distributions were quasi-specular and scattered rotational distributions were strongly dependent upon the incidence energy, both observations indicating the direct nature of the interaction. The most important observation of the work was the approximately Arrhenius surface temperature dependence of the vibrational excitation probability, exhibiting an effective activation energy close to the vibrational excitation energy of the scattered molecule (see Fig. 2). The authors also showed that the... 

The relative shift of the peak position of the rotational distribution in the presence of a vector potential thus confirms the effect of the geometric phase for the D + H2 system displaying conical intersections. The most important aspect of our calculation is that we can also see this effect by using classical mechanics and, with respect to the quantum mechanical calculation, the computer time is almost negligible in our calculation. This observation is important for heavier systems, where the quantum calculations are even more troublesome and where the use of classical mechanics is also more justified. 

Witting and coworkers (1988) used laser (193 nm) to photo dissociate HBr in a C02-HBr van der Waal complex and monitored the OH rotational distribution arising out of the reaction... 

Representative TOF spectra following 532 nm heating pulses for three different rotational states of NO are presented in Fig. 8. These spectra appeared to consist of contributions from two distinct desorption channels a slow thermal channel and a fast non-Boltzmann channel. The distinctly different rotational distributions observed for these two components (see below) provided additional support for such an interpretation. 

This is, however, only the contribution of a rigidly rotating distribution of electrons and predictions of the g factor based on this expression [41,42] do not agree with the experiment [42]. It is therefore necessary to take into account that the motion of the electrons is perturbed by the rotation of the molecule [16 17,42], i.e., electronic motion and molecular rotation couple through which... 

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