ANGULAR-DISTRIBUTIONS OF PHOTOELECTRONS FROM MULTIRESONANT IONIZATION OF ATOMIC-HYDROGEN AT 608 NM

An all-order multiphoton resonant theory is presented within the resolvent formalism. Previous operator expressions obtained in the single-resonance case are generalized to multiresonance problems. The theory is applied to the calculation of angular distributions of photoelectrons arising from the ionization of hydrogen by a realistic light pulse of 0.7-psec duration at 608 nm. For intensities greater than 1.9 × 1013 W/cm2, the computation shows that we have not a seven- but an eight-photon ionization process. The ac Stark shift of atomic levels generates induced resonances above the atomic ionization limit. The effect of such resonances on the angular distributions of photoelectrons is discussed. The inspection of the total electron yield proves that the F-state resonances prevail over the P-state ones. © 1990 Optical Society of America.