Overtone state

Tables for all degenerate point groups, giving the symmetry species of vibrational combination states resulting from the excitation of one quantum of each of two different degenerate vibrations and of vibrational overtone states resulting from the excitation of two quanta of the same degenerate vibration, are given in the books by Herzberg and by Hollas, referred to in the bibliography.

An example of an application to actual spectroscopy is shown in Figure 6.9. This shows the states computed in the range of the 0 —> 3 CH spectral transition. The intensities were computed as a Franck-Condon overlap of the optically bright CH overtone state (Holme and Levine, 1989 Levine and Berry, 1989) with the relevant eigenstate. 

The earlier discussion focused on the v = 0 and v = 1 vibrational states. However, in a high-order experiment, higher vibrational states must be considered as well. In fact, if the vibration is purely harmonic, the Raman echo signal is exactly canceled by additional processes involving the overtone states (56-60). Thus, anharmonicity in the vibration is essential. As the difference between the 0 -> 1 and 1 2 transition frequencies... 

In local-mode sampling an individual local mode such as a CH bond in benzene is excited [28]. This type of trajectory calculation has been performed to determine the population of a local-mode state a) versus time, from which the absorption linewidth of the overtone state may be determined [29]. Good agreement has been found with both experimental and quantum mechanically calculated overtone linewidths for benzene [30] and linear alkanes [31]. 

The survival probability for the n = 3 overtone of benzene has been determined by a time-dependent quantum mechanical calculation based on a 16-mode planar benzene model (5 CH stretch modes are inactive out of the 21 planar modes). All states for these modes are treated in the calculation. The = 3 zero-order overtone state is assumed to be a state with three quanta in one C—H internal coordinate (i.e., a local mode). The quantum survival probability is plotted in figure 4.13. It is similar to the experimental P (t) in that there is a rapid fall-olT at short times, followed by multiple small recurrences. This agreement supports the interpretation that the broad absorption... 

The model in figure 4.14 results from a 2 1 bend-stretch Fermi resonance model for IVR from benzene overtone states (Sibert et al., 1984a). The first tier is a group of states for which one quantum of CH stretch, Wch. has been transferred to two quanta of CH bend, n. In the second tier an additional cn quantum has been transferred to two more quanta. Though this model is based on strong physical arguments, it is still not known whether this Fermi resonance and tier model is the complete picture for IVR in benzene. 

Quack and co-workers (Segall et al., 1987 Baggott et al., 1985 Marquardt and Quack, 1991) have solved Eqs. (4.13)-(4.17) for CH overtone states in a variety of molecules including CF3H, CD3H, and They used the tridiagonal zero-... 

The apparatus for one of the first pump probe experiment is shown in Figure 5.19 (Rizzo et al., 1984). It was used to study the dissociation rate of overtone excited HOOH and r-butyl hydrogen peroxide, both of which lose an OH radical (Rizzo and Crim, 1982 Ticich et al., 1986 Rizzo et al., 1983, 1984). The Nd YAG-pumped dye laser was used to excite the molecule (in a bulb) to selected overtone states, while the nitrogen laser pumped dye laser was used to probe the product OH radicals by laser fluorescence excitation as a function of delay time. 

Fermi resonance between ring fundamental and overtone State of tyrosine —OH /jso/ /g3o = 9 10 to 10 3, H bond from acidic proton donor 10 9 to 3 10, strong —OH bond to negative proton acceptor 47... 

Puttkamer and Quackl 195 have obtained lower bounds for the lifetimes of the first and second overtone states and these are listed in rows 4 and 5 of Table V. In a very recent paper 1 they revised the estimate for vj = 2, K = 0 to > 0.05 ns and pointed out a less likely assignment by which the lifetime might be as short as 0.01 ns for vi = 2, K = 2. Most recently, Fraser and Pine measured the predissociation lifetime of HF... DF... 

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