ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The detailed level-by-level fitting of spectra of systems with strongly chaotic classical dynamics is investigated. Fitting of these "unassignable chaotic spectra'' is advocated as a desirable counterpart to statistical analysis, giving a detailed probe of molecular potential surfaces and intramolecular dynamics, including phase-space "bottlenecks.'' The role of "assigning'' levels in a spectral fit is discussed. It is concluded that what is really necessary for fitting is to "label'' the spectrum, in a sense made precise. There is no barrier, in principle, to fitting chaotic spectra that may be unassignable in terms of the usual zero-order quantum numbers such as normal modes. The difficulties introduced into the labeling process by experimental factors of spectral resolution and sensitivity are considered. The occurrence of missing levels or features is identified as the key labeling problem. A "bootstrap'' method is introduced to label and fit a spectrum with missing levels. The "bootstrap'' method works by using the knowledge obtained at each energy range of the fit to successively label and fit higher energies. The bootstrap method is tested on simulated experimental spectra. A program called fitter uses the bootstrap procedure successfully to identify missing levels, label and fit the spectrum, [AV:and reproduce the molecular potential. The occurrence of doublets in highly excited spectra is noted as possible spectral evidence of a bottleneck giving rise to chaotic local modes. Fitting of large-scale "clump'' features is discussed as a means to probe energy flow dynamics and potentials of "doorway'' modes of molecules. Fitting of features or individual levels on successively finer energy scales is discussed as a probe of subsequent energy flow dynamics through "interior'' modes.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.459588
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