Alignment of the E,F 1Σ+g, v'E=1 state of H2 by two-photon excitation

The alignment of the E,F 1Σ+g, v'E=1 state of H2 produced by two-photon excitation from the X 1Σ+g, v double-prime=0 ground state was investigated using two different techniques. First, in a single-color experiment, photoelectron angular distributions were measured for the two-photon resonant, three-photon ionization of H2 via the Q(0) and Q(1) transitions to the E,F 1Σ+g, v'E=1 state. The photoelectron angular distributions are consistent with an unaligned E,F 1Σ+g, v'E=1, J'=1 state. Second, in a two-color experiment, the photoionization spectra of several vibrationally autoionizing (X 2Σ+g)np, v=1 Rydberg states excited from the v'E=1, J'=1 level of the E,F 1Σ+g state were measured as a function of the relative polarizations of the pump and probe beams. The polarization dependence of the relative intensities of the P(1) and Q(1) transitions was used to determine the alignment of the E,F 1Σ+g, v'E=1, J'=1 state produced by the pump laser. Consistent with the angular distribution measurements, the polarization results indicate that the populations in the M'=0 and M'=±1 levels of the E,F 1Σ+g, v'E=1, J'=1 state are equal, within the experimental uncertainty of 15%