Semiclassical nonlinear response functions for coupled anharmonic vibrations

Journal Article · Sat Nov 28 04:00:00 EST 2009 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.3266566· OSTI ID:21559809

Gruenbaum, Scott M; Loring, Roger F ^[1]

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1. Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853 (United States)

Observables in linear and nonlinear infrared spectroscopy may be computed from vibrational response functions describing nuclear dynamics on a single electronic surface. We demonstrate that the Herman-Kluk (HK) semiclassical approximation to the quantum propagator yields an accurate representation of quantum coherence effects in linear and nonlinear response functions for coupled anharmonic oscillators. A considerable numerical price is paid for this accuracy; the calculation requires a multidimensional integral over a highly oscillatory integrand that also grows without bound as a function of evolution times. The interference among classical trajectories in the HK approximation produces quantization of good action variables. By treating this interference analytically, we develop a mean-trajectory (MT) approximation that requires only the propagation of classical trajectories linked by transitions in action. The MT approximation accurately reproduces coherence effects in response functions of coupled anharmonic oscillators in a regime in which the observables are strongly influenced by these interactions among vibrations.

• OSTI ID: 21559809
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 20 Vol. 131; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABSORPTION SPECTROSCOPY
ACCURACY
ANHARMONIC OSCILLATORS
APPROXIMATIONS
CALCULATION METHODS
FUNCTIONS
HARMONIC OSCILLATORS
INFRARED SPECTRA
INTERACTIONS
INTERFERENCE
NONLINEAR PROBLEMS
PROPAGATOR
QUANTIZATION
RESPONSE FUNCTIONS
SEMICLASSICAL APPROXIMATION
SPECTRA
SPECTROSCOPY
TRAJECTORIES