Collision-induced spectroscopy with long-range intermolecular interactions: A diagrammatic representation and the invariant form of the induced properties
- Institute of Physics, Saint Petersburg State University, Ulyanovskaya str. 1, Peterhof, Saint Petersburg 195904 (Russian Federation)
Collision-induced properties of two interacting molecules a and b are derived by means of a general diagrammatic method involving M molecule-molecule and N photon-molecule couplings. The method is an extension of previous graphical treatments of nonlinear optics because it exhaustively determines interaction-induced polarization mechanisms in a trustworthy and handy fashion. Here we focus on long-range intermolecular interactions. Retardation effects are neglected. A fully quantum-mechanical treatment of the molecules is made whereas second quantization for the electromagnetic field, in the nonrelativistic approximation, is implicitly applied. The collision-induced absorption, Raman, and hyper-Raman processes are viewed and studied, through guiding examples, as specific cases N=1, 2, and 3, respectively. In Raman (N=2), the standard first-order (M=1) dipole-induced dipole term of the incremental polarizability, {delta}{alpha}, is the result of a coupling of the two photons with distinct molecules, a and b, which perturb each other via a dipole-dipole mechanism. Rather, when the two photons interact with the same molecule, a or b, the (N=2, M=1) graphs predict the occurrence of a nonlinear polarization mechanism. The latter is expected to contribute substantially to the collision-induced Raman bands by certain molecular gases.
- OSTI ID:
- 20852927
- Journal Information:
- Physical Review. A, Journal Name: Physical Review. A Journal Issue: 1 Vol. 74; ISSN 1050-2947; ISSN PLRAAN
- Country of Publication:
- United States
- Language:
- English
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