Vibrational lines

Muller L J, Vanden Bout D and Berg M 1993 Broadening of vibrational lines by attractive forces ultrafast Raman echo experiments in a CH2l CDCl2 mixture J. Chem. Phys. 99 810-19... 

The molecule HgH has vibrational lines at 1204, 966, 632, and 172 cm . Constiuct the Birge-Spooner plot for this molecule and find its dissociation energy Dq and bond energy Dg. 

The produet of these 3-j symbols is nonvanishing only under eertain eonditions that provide the rotational seleetion rules applieable to vibrational lines of symmetrie and spherieal top moleeules. 

The molecular structures were rendered with good-quality shading on a blue background. Isosurfaces produced from cube files or checkpoint files also looked nice. Molecular vibrations can be animated on screen and vibrational displacement vectors displayed. The vibrational line spectrum may be displayed too, but the user has no control over the axes. There is no way to set the background color. The display can be saved using several image file formats. 

Madden P. A., Lynden-Bell R. M. Theory of vibrational line-widths,... 

Strekalov M. L., Burshtein A. I. Theory of vibrational line width in dense gases, Chem. Phys. 82, 11-24 (1983). 

We will first describe the results obtained for n-type GaAs doped with silicon and then those on p-type GaAs and InP, trying to show how the spectroscopic results correlate with the electrical measurements to provide a consistent picture of the neutralization of dopants by hydrogen in III-V semiconductors. After considerations on the temperature dependence of the widths and positions of the H-related lines, we will discuss the occurrence and origin of other vibration lines associated also with hydrogen in as grown bulk and epitaxial III-V compounds. 

In InP Zn samples purposely neutralized by hydrogen, a sharp vibrational line is observed at LHeT at 2287.7 cm-1 shifting to 1664.5 cm-1 in deuterated samples (Pajot et al., 1989). The r-factor for these lines (1.3744) and the frequencies indicate that P—H or P—D bonds have been formed and that the neutralizing complex is presumably (P—H Zn). 

VIBRATIONAL LINE SHAPES, SPECTRAL DIFFUSION, AND HYDROGEN BONDING IN LIQUID WATER... 

Vibrational spectroscopy can help us escape from this predicament due to the exquisite sensitivity of vibrational frequencies, particularly of the OH stretch, to local molecular environments. Thus, very roughly, one can think of the infrared or Raman spectrum of liquid water as reflecting the distribution of vibrational frequencies sampled by the ensemble of molecules, which reflects the distribution of local molecular environments. This picture is oversimplified, in part as a result of the phenomenon of motional narrowing The vibrational frequencies fluctuate in time (as local molecular environments rearrange), which causes the line shape to be narrower than the distribution of frequencies [3]. Thus in principle, in addition to information about liquid structure, one can obtain information about molecular dynamics from vibrational line shapes. In practice, however, it is often hard to extract this information. Recent and important advances in ultrafast vibrational spectroscopy provide much more useful methods for probing dynamic frequency fluctuations, a process often referred to as spectral diffusion. Ultrafast vibrational spectroscopy of water has also been used to probe molecular rotation and vibrational energy relaxation. The latter process, while fundamental and important, will not be discussed in this chapter, but instead will be covered in a separate review [4],... 

In addition to the effects of motional narrowing, vibrational line shapes for the OH stretch region of water are complicated by intramolecular and intermolecular vibrational coupling. This is because (in a zeroth-order local-mode picture) all OH stretch transition frequencies in the liquid are degenerate, and so the effects of any... 

A number of researchers [15, 38 40, 43, 113, 124 126, 128, 146] have used mixed quantum/classical models, mostly as described in Section III.A, to calculate vibrational line shapes for this system, and several are in fair agreement with experiment. Here we describe our latest work involving approaches discussed in Section III.C. Our theoretical line shapes are calculated as briefly described in previous sections and in published work [98]. From an MD simulation of SPC/E heavy water, we determine the electric field on each putative H atom. We then use electric field maps to determine the transition frequency and dipole derivative. The orientational contribution to mp(t) we... 

As evidenced from the above discussion, vibrational line shapes provide information mostly about intermolecular structure. Transient hole burning and more recently echo experiments, on the other hand, can provide information about the dynamics of spectral diffusion. The first echo experiments on the HOD/ D2O system involved two excitation pulses, and the signal was detected either by integrating the intensity [20] or by heterodyning [22]. The experiments were analyzed with the standard model assuming Gaussian frequency fluctuations. The data were consistent with a spectral diffusion TCF that was bi-exponential, involving fast and slow times of about 100 fs and 1 ps, respectively. 

We have described our most recent efforts to calculate vibrational line shapes for liquid water and its isotopic variants under ambient conditions, as well as to calculate ultrafast observables capable of shedding light on spectral diffusion dynamics, and we have endeavored to interpret line shapes and spectral diffusion in terms of hydrogen bonding in the liquid. Our approach uses conventional classical effective two-body simulation potentials, coupled with more sophisticated quantum chemistry-based techniques for obtaining transition frequencies, transition dipoles and polarizabilities, and intramolecular and intermolecular couplings. In addition, we have used the recently developed time-averaging approximation to calculate Raman and IR line shapes for H20 (which involves... 

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