Polyatomics, highly excited

Oref I and Tardy D 0 1990 Energy transfer in highly excited large polyatomic molecules Chem. Rev. 90 1407 5... 

Hippier H, Troe J and Wendelken H J 1983 Collisional deactivation of vibrationally highly excited polyatomic molecules. II. Direct observations for excited toluene J. Chem. Phys. 78 6709... 

Oref I and Rabinovitch B S 1979 Do highly excited polyatomic molecules behave ergodically Acc. Chem. Res. 12 166-75... 

Abstract. The development of modern spectroscopic techniques and efficient computational methods have allowed a detailed investigation of highly excited vibrational states of small polyatomic molecules. As excitation energy increases, molecular motion becomes chaotic and nonlinear techniques can be applied to their analysis. The corresponding spectra get also complicated, but some interesting low resolution features can be understood simply in terms of classical periodic motions. In this chapter we describe some techniques to systematically construct quantum wave functions localized on specific periodic orbits, and analyze their main characteristics. 

It is not possible to discuss highly excited states of molecules without reference to the recent progress in nonlinear dynamics.2 Indeed, the stimulation is mutual. Rovibrational spectra of polyatomic molecules provides both an ideal testing ground for the recent ideas on the manifestation of chaos in Hamiltonian systems and in turn provides many challenges for the theory. 

The results show that collisional transfer is very efficient from a molecule in the highly excited and closely spaced quantum states, which behave as a classical system with little restriction due to quantisation. The monatomic and diatomic gases appear to be rather less effective than the polyatomic molecules, which may emphasise the importance of V-V transfer in this type of process. However, it is desirable to establish experimentally how the energy is distributed in both molecules following collision. 

Multiphoton ionization (MPI) has become an important technique for the study of highly excited electronic states (e.g., Rydberg states in polyatomic molecules) or states not accessible by one-photon absorption. Some studies that have made use of simultaneous absorption of more than one photon by the species of interest have already been mentioned in previous sections, particularly if the non-linear absorption leads to fluorescence. Table 6 provides details of remaining articles dealing with multiphoton spectroscopy and MPI. 

Robin, M.B. (1974/1985), Highly Excited States of Polyatomic Molecules, Vol. 1-3 Academic Press New York. 

E.E.Nikitin, Vibrational relaxation of highly-excited polyatomic molecules, Doklady Akad.Nauk SSSR, 239, 380 (1978)... 

E.l.Dashevskaya, E.E.Nikitin, and I.Oref, On the adiabaticity restrictions in the collisional energy transfer from highly excited polyatomic molecules, J. Phys. Chem. 97, 9397 (1993)... 

This chapter is devoted to recent developments in a class of approximation methods that aim at describing the energy-level structure and dynamics of energy transfer in vibrationally highly excited polyatomic systems. The meth ods that are the subject of the present study are the self-consistent-field (SCF) approximations, in which framework each vibrational mode is described as moving in an effective field obtained by averaging the full potential function... 

The previous sections indicate that the full quantum dynamical treatment of IVR in an intermediate size molecule even under conditions of coherent excitation shows phenomena reminiscent of relaxation and equilibration. This suggests that, in general, at very high excitations in large polyatomic molecules with densities of states easily exceeding the order of 10 cm (or about 10 molecular states in an energy interval corresponding to 1 J moP ), a statistical master equation treatment may be possible [38, 122]. Such an approach has been justified by quantum simulations in model systems as well as analytical considerations... 

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