Angle resolved photoelectron spectroscopy of O-2(a(1)Delta(g)) with synchrotron radiation

Angular distribution of photoelectrons for the photoionization processes O- 2(+)(X (2)Pi(g), upsilon(+) = 0-3) + e(-) <-- O-2(a(1) Delta(g)) + h nu has been studied at the photon energy of 21.22 eV and in the photon energy ran ge 13.8-15.2 eV where the cross-sections for these processes show strong en hancement due to the presence of resonant transitions to a Rydberg state (C (2)Phi(u),3s sigma(g))p (1)Phi(u). It has been found that the plot of the asymmetry parameter, beta, against photon energy shows structure at energie s corresponding to O-2(p (1)Phi(u)upsilon(')) <-- O-2(a (1)Delta(g)upsilon " = 0) excitations. The O-2(+)(X (2)Pi(g),upsilon(+)) <-- O-2(a (1)Delta(g) ,upsilon " = 0) ionizations have also been investigated in the photon energ y range 18.0-19.2 eV, where the presence of unassigned resonances was obser ved in earlier photoelectron spectroscopic work. In this energy range the p lot of asymmetry parameter against photon energy also shows resonant struct ure. Suggestions for the excited states associated with these resonances ha ve been made on the basis of constant-ionic-state spectra recorded at diffe rent angles. (C) 2000 American Institute of Physics. [S0021-9606(00)02703-3 ].