Lifetimes of Excited Alkalilike Atoms Colliding by Van der Waals Forces with Inert Gas Atoms in the Groundstate

Abstract

The influence of Van der Wads forces on the lifetime of coherently excited hyperfine-states IFpF;) and I F p i $ ) of alkalilike atoms i by collissions with inert gas atomsj in the groundstale IFimpi) has been examined. To do this the timedependent Schrodinger equation has been solved on taking into account a static magnetic field, a radiation field and a Van der Wads force. Introducing an impact parameter model for the colliding atoms with small scattering angles which form a quasimolecule Jp> = IFimFiFimFi> an expression for the cross section uFFp has been derived which determines the halfwidth rFpt of the coherently excited states. On making use of the irreducible tensor representation the calculation of the cross-section has been reduced to the calculation of multipole transitions. The result has been applied e.g. to the coherently excited 3dl04~2P~,~-states of Cu I colliding by dipole-dipole interactions with inert gas atom's He I, Ne I and Ar I in the ground state.The values agree well with data which have been derived from zero-level-crossing experiments.