Predissociation resonance energy

Complex-Coordinate Coupled-Channel (CCCC) methods are presented for the accurate and efficient treatment of the resonance energies and widths (lifetimes) of multichannel rotatlonally predissociating van der Waals (vdW) molecule resonances. Algorithms for dealing with the complex scaling of numerical and piecewise analytical potentials are also presented. 

The results de scribed in this paper for vdU molecule predissociation demonstrate that the CCCC formalisms provide accurate and efficient methods for the direct prediction of resonance energies and widths of metastable states. In work published elsewhere (36), the CCCC oiethod has also been extended and applied to the first determination of the energies and widths of the autolonlzing resonances of the hydrogen atom in intense magnetic fields. The utility and advantages of the CCCC methods may be sunmarlzed as follows (1) It is an ab initio method (given a defined "exact" hamiltonlan). (2) Only... 

For E = Er (the energy including the predissociation-induced energy shift, called the resonance energy), the absorption has its maximum value, aa(Er) =... 

Molecular applications have thus far involved the calculation of the electronic structure and potential energy surfaces of negative ion "compound states" and of "diabatic states" in the continuous spectrum of polyelectronic diatomics and triatomics and of energies and partial widths with interchannel coupling of vibrational shape and predissociating resonances of diatomics. The same principles and methodologies can be applied to many more such cases. 

Table 1 Resonance properties calculated for Cl + HF(v = 0) collisions. The resonance energies, in kcal/mol, and lifetimes (ps) are obtained from the largest eigenvalue of the Q-matrix and the product distribution (partial width ratio Fi/F) is obtained from the square of its eigenvectors. The assignments based on the rotational predissociation model (vj , v/, /) as well the model results, given in parenthesis, are also presented. The results are for the —29.3 to - 28.5 kcal/mol range measured with respect to the zero point energy of the F + HCl(v = 0). This corresponds to 3.3 to 4.01 kcal/mol measured from Cl- -HF(v = 0) and is the range given in Fig. 4.

Perhaps the most pertinent observation to make at this point is that the process by which the molecule with energy spectrum hypothesized decays is simply a form of predissociation. There is one difference between the process we consider and the usual case of predissociation from a single zero-order molecular energy level. Because the exact resonant level is represented as a linear combination of the zero-order localized level, the... 

In closing the section on non-Hermitean approaches to continuum processes in atomic and molecular physics, we will also mention accurate examinations on resonance parameters in molecular predissociation displaying unexpected resonance overlapping [46,89]. The phenomenon of predissociation by rotation in HgH was analyzed via an isotopically combined potential due to Stwalley [120]. The potential, i.e., a relatively shallow energy curve with a nonzero /-value giving rise to a rotational barrier, supported novel metastable states above the dissociation limit. The Weyl s method was able to resolve the closely lying vibrational states v = 3 and v = 4 for the rotational quantum number K = 9. 

This kind of resonance structure in the predissociation of HNO has also been seen in experiment [266], however, at values of J which differ considerably from those obtained in the dynamics calculations. A quantitative description of these mixing effects requires very accurate PES s, because the level structure — in the case of HNO the level structure of two different electronic states — has to be precisely reproduced. The two calculated potentials for HNO do not meet this requirement for example the vertical energy separation is wrong by about 0.1 eV. 

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