Semiclassical many-mode Floquet theory. II. Non-linear multiphoton dynamics of a two-level system in a strong bichromatic field
Journal
Journal of Physics B: Atomic and Molecular Physics
Journal Volume
17
Journal Issue
10
Pages
2101-2128
Date Issued
1984
Author(s)
Ho, T.-S.
Abstract
For pt.I see Chem. Phys. Lett. vol.96, p.464 (1983). The non-linear multiphoton excitation dynamics of two-level systems under the influence of two strong linearly polarised monochromatic fields is studied exactly for the first time along the semiclassical many-mode Floquet theory. The present approach relaxes the restrictions of the conventional generalised rotating-wave approximation (GRWA) and allows correct treatment of various non-linear features such as power broadening, resonance shift, asymmetry in absorption lineshape, etc. By extending the nearly degenerate perturbative method of Salwen (1955), approximate analytical expressions for transition probabilities are obtained for multiphoton resonance processes for which (n+1) photons of one field are absorbed, whereas n photons of the other field are emitted, where n is an arbitrary integer. Detailed comparison of the analytical, the GRWA and the numerically exact results is given. Also presented is a case study of the time evolution of spin 1 / 2 systems in multi-quantum NMR transitions driven by pulsed bichromatic radiofrequency fields.
Type
journal article