Double- and Triple-Photon Decay of MetastableP03Atomic States

The radiative decay of metastable nsnp ${}_{}{}^3{}_{}{}^{}P_0^{}{}_{}{}^{}$ atomic states is found to occur only by odd-parity multiphoton modes such as $E1M1\mathrm{}$ and $3E1$, in the absence of hyperfine structure. A detailed calculation of the $E1M1\mathrm{}$ rates for several members of the Be sequence is presented, in the nonrelativistic approximation. Only the general properties of $3E1$ decay are presented. Among other results, the $3E1$ rate is found to be zero if any two photons have the same energy, and its spectrum, unlike the symmetrical two-photon spectra, is found to be irregular and asymmetric, being peaked somewhat below half the transition energy.