LOCALIZATION OF A CONTINUUM SHAPE RESONANCE - PHOTOIONIZATION OF CS2

We report a vibrationally resolved investigation into the 5sigma(u)-1 shape-resonant ionization dynamics for CS2 in the range 18 less-than-or-equal-to hnu less-than-or-equal-to 30 eV. The intensity of dispersed fluorescence from CS2+(B2SIGMA(u)+) photoions is measured to obtain partial photoionization cross-section curves for the v = (0,0,0) and (1,0,0) levels of CS2+(B2SIGMA(u)+), as well as the vibrational branching ratio. Our results indicate a shape resonance at hnu almost-equal-to 21 eV which is insensitive to changes in the symmetric stretching coordinate. These data are consistent with recent theoretical efforts that predict a shape resonance in the 5sigma(u) --> epsilonpi(g) channel. All previous vibrationally resolved data on shape resonances have been obtained for systems whose shape resonances occur in the epsilonsigma continuum. The current results are in contrast to behavior observed for other shape resonances, highlighting both their diverse nature and possible extensions of the current measurements.