The electron angular distribution of different rotational branches in the VUV photoelectron spectrum of H2

By high-resolution photoelectron spectrometry using a cooled H2(upsilon''=0, J''=0, 1) target beam, the relative intensities of the Q and S rotational branches have been determined for several H2+(upsilon') vibrational states at photon wavelengths of 58.4, 73.6 and 74.4 nm. From results measured at different angles between the direction of the unpolarised photon beam and the momentum of the ejected electrons, the angular anisotropy parameter #betta#sub(s) has been determined for S-branch electrons (δJ=2 transitions), and it has been found that (e.g. for upsilon'=0) #betta#sub(s)(58.4 nm)=0.81(17), #betta#sub(s)(73.6 nm)=0.54(16) and #betta#sub(s)(74.4 nm)=0.76(27). These data show that at photoelectron energies of 5 eV and 1 eV the contribution due to f-electron waves cannot b ignored. A search for δJ=4 transitions at 58.4 nm has yielded an upper limit of 0.3% with respect to the δJ=0 partial cross section. (author)