A theoretical study of the two-photon ionization of metastable He with linearly and circularly polarized laser light

Generalized cross sections
\hat{\sigma}_{L}
and
\hat{\sigma}_{C}
for the two-photon ionization of He from the metastable
2^{1}S
state are calculated for linearly and circularly polarized incident laser light, respectively, in the wavelength range 3725-5100 Å. Significant enhancement of cross sections occurs through real
3^{1}P
and
4^{1}P
p intermediate states. The ratio
\hat{\sigma}_{C}
/
\hat{\sigma}_{L}
shows a minima at the wavelengths close to 3743 and 4450 Å.