We calculate the selection rules for single photonic transitions in hydrogen- like atoms. We show that for the first part the reduced selection rules read: . For the second part the reduced selection rules read:
A theoretical investigation of the three-photon transition rates $2\phantom{\rule{0.16em}{0ex}}{}^{1}{P}_{1}\ensuremath{\rightarrow}2\phantom{\rule{0.16em}{0ex}}{}^{1}{S}_{0}\phantom{\rule{0.28em}{0ex}},1\phantom{\rule{0.16em}{0ex}}{}^{1}{S}_{0}$ and $2\phantom{\rule{0.16em}{0ex}}{}^{3}{P}_{2}\ensuremath{\rightarrow}2\phantom{\rule{0.16em}{0ex}}{}^{1}{S}_{0}\phantom{\rule{0.28em}{0ex}},1\phantom{\rule{0.16em}{0ex}}{}^{1}{S}_{0}$ for the helium atom is presented. Photon energy distributions and precise values of the nonrelativistic transition rates are obtained with employment of correlated wave functions of the Hylleraas type. The possible experiments for the tests of the Bose-Einstein statistics for multiphoton systems are discussed.
Selective multiphoton excitations can be achieved by tailoring the driving pulses to manipulate the outcome of the light-matter interaction. While single-photon transitions of single atoms driven by ultrashort pulses, dependent mainly on the resonant frequency component, and thus possesses no optical selectivity no matter how the excitation pulse shapes [1]. Interestingly, when an ultrashort pulse interacts with an optically dense medium, quantum controllable optical selectivity can be achieved in a single-photon process.