Dichromatic polyphotonic ionization rate of He for lambda(1)=248 nm and lambda(2)=(1/3)248 nm from the many-electron, many-photon theory

By extending and implementing the many-electron, many-photon theory (MEMPT) to the dichromatic case with commensurate frequencies, we computed multiph oton ionization rates of He for experimentally realizable situations. Speci fically, lambda (1) = 248 nm and lambda (2) = (1/3)248 nm with I-1 = 1 x 10 (14) Wcm(-2) and I-2 = 1 x 10(10), 1 x 10(12) and 1 x 10(13) Wcm(-2). For I -2 = 1 X 10(12) W cm(-2), we present the curve of the rate as a function of the phase difference, phi, from 0 to 2 pi. For the other cases, we report the rates for phi = 0 and pi and we compare the MEMPT complex eigenvalues w ith those obtained by Telnov and Chu (1998 Int. J. Quantum Chem. 69 305) wh o used a generalized Floquet formulation of the time-dependent density func tional theory at the independent-particle level. The effect of electron cor relation, which is included in the MEMPT, is quantitative. Specifically, co mpared with the results of Telnov and Chu the MEMPT energies are lower by 0 .04 au and the rates are larger by a factor of three.