Jet-like structures in photoelectron angular distributions

The photoelectron angular distributions (PADs) of hydrogenatoms in an intense laser field of linear polarization are studiedusing the S-matrix theory in the length gauge. The PADs show mainlobes along the laser polarization and jet-like structures stickingfrom the waist of main lobes. Our previous prediction, based on anonperturbative scattering theory of photoionization developed byGuo et al, showing that the number of jets on one side of PADsmay increase by one, three, or other odd numbers and may decrease by onewhen one more photon is absorbed, is confirmed by this treatment.Within the strong-field approximation, good agreement is obtainedbetween these two quite different treatments. We further study theinfluence of the Coulomb attraction to PADs, by taking aCoulomb--Volkov state as the continuum state of photoelectrons. Wefind that under the influence of the Coulomb attraction, the PADschange greatly but the predicted phenomena still appear. This studyverifies that the jet-like structures have no relation with theangular momentum of photoelectrons.