PUB - Publikationen an der Universität Bielefeld

We derive a "master" perturbation series for the quantum amplitude for a given transition process induced by laser-matter interaction. The result is derived using a complete set of basis functions depending on a real parameter lambda. It provides a one-parameter (lambda) family of infinitely many equivalent series representations of one and the same transition amplitude defined in the minimal coupling (MC) "velocity gauge". As a first application of the master series we put lambda = 0 and 1 in the formula and immediately obtain the two well-known perturbation series, traditionally derived in the "velocity" and "length" gauges. The master formula can be used to obtain any number of equivalent perturbation series by simply choosing a real number for lambda; e.g., a "hybrid perturbation" series follows from putting lambda = 1/2 in the formula.