Classical sudden model for vibrational and rotational excitations in ion-molecule collisions
- Institute of Space and Astronautical Science, Sagamihara 229-8510 (Japan)
- College of Science and Technology, Nihon University, Funabashi 274-8501 (Japan)
We develop a classical model of an ideally sudden character for vibrational and rotational excitations in collisions of an atom (or an ion) with a diatomic molecule at energies as high as 10-10{sup 2} eV. The energy-loss spectra with vibrotational levels left unresolved are analytically expressed with a repulsive intermolecular potential in a hard potential limit (i.e., a vanishing range of force). It turns out to be an extension of the hard shell model for a rigid-rotor molecule developed by Beck et al. two decades ago. For a homonuclear molecule, the hard potential model generally derives spectra with double peaks at both edges, one nearly elastic and another deeply inelastic. They are analogous to rotational rainbows though their positions are affected by vibrational excitation. Classical trajectory calculations with a finite-range model potential are carried out for collision systems of H{sup +}+N{sub 2} and Li{sup +}+N{sub 2}, and systematically compared with the model. It is found that the effect of vibrational excitation manifests itself the way the model predicts. It is also demonstrated that the spectra are virtually reduced to the hard potential model when the vibrational period is artificially taken much longer than a collision time, while reduced to the hard shell model when much shorter.
- OSTI ID:
- 20640739
- Journal Information:
- Physical Review. A, Vol. 69, Issue 2; Other Information: DOI: 10.1103/PhysRevA.69.022716; (c) 2004 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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