arXiv subjects

John S Briggs

Publications and source records attributed to John S Briggs.

2 recordsLinked to original sources

arXiv2016

The cross-over from tunnelling to multiphoton ionization of atoms

We present a theory illuminating the cross-over from strong-field tunnelling ionization to weak-field multiphoton ionization in the interaction of a classical laser field with a hydrogen atom. A simple formula is derived in which the ionization amplitude appears as a product of two separate amplitudes. The first describes the initial polarization of the atom by virtual multiphoton absorption and the second the subsequent tunnelling out of the polarized atom. Tunnelling directly from the ground state and multiphoton absorption without tunnelling appear naturally as the limits of the theory.

physics.atom-ph↗

arXiv1999

Time Dependence in Quantum Mechanics

It is shown that the time-dependent equations (Schrödinger and Dirac) for a quantum system can be always derived from the time-independent equation for the larger object of the system interacting with its environment, in the limit that the dynamical variables of the environment can be treated semiclassically. The time which describes the quantum evolution is then provided parametrically by the classical evolution of the environment variables. The method used is a generalization of that known for a long time in the field of ion-atom collisions, where it appears as a transition from the full quantum mechanical {\it perturbed stationary states} to the {impact parameter} method in which the projectile ion beam is treated classically.

quant-ph↗