ANGLE-RESOLVED PHOTOELECTRON-SPECTRUM OF ROTATIONAL STATES IN H-2(+)

We have recorded an angle-resolved photoelectron spectrum of the first four vibrational peaks of the X (2)Sigma(g)(+) state of H-2(+). In th e spectrum, the individual peaks of the Delta N=0 rotational branch ar e completely resolved. From curve fitting of the rotational branches, we found the anisotropy parameter of the /<(mu)over bar>(0,0)/(2) squa red reduced multipole moment matrix element to be beta=1.85, with no s ignificant difference between the vibrational states. For the /<(mu)ov er bar>(2,0)/(2) squared reduced multipole moment matrix element, we f ound beta(v=0) = 0.83, decreasing slightly at higher vibrational level s. The earlier observed increase in the beta parameter with vibrationa l quantum number is mainly explained by a decreased size of /<(mu)over bar>(2,0)/(2) relative to /<(mu)over bar>(0,0)/(2), dominating the be ta decrease of the /<(mu)over bar>(2,0)/(2) squared reduced multipole moment matrix element itself. We have also determined the beta value o f individual peaks in the Delta N=0 branch. The difference in beta bet ween the peaks in this branch is small. In particular, the 0-0 transit ion does not seem to have a considerably higher beta value than the ot her members of the Delta N=0 branch, which is expected from theory.