Dissociative multiple photoionization of Br2, IBr, and I2 in the VUV and X-ray regions:: a comparative study of the inner-shell processes involving Br(3d,3p,3s) and I(4d,4p,4s,3d,3p)

Dissociative multiple photoionization of the bromine, the iodine monobromide, and the iodine molecules in the Br(3d,3p,3s) and 1(4d,4p,4s,3d,3p) inner-shell regions has been studied by using time-of-flight (TOF) mass spectrometry coupled to synchrotron radiation in the ranges of 90similar to978 eV for Br-2 60similar to133 eV for IBr, and 86similar to998 eV for 1, Total photoion and photoion-photoion coincidence (PIPICO) yields have been recorded as functions of the photon energy. Here, giant shape resonances have been observed beyond the thresholds of the inner-shells owing to the Br(3d(10))-->Br(3d(9)epsilonf), I(4d(10))-->I(4d(9)epsilonf), and I(3d(10))-->I(3d(9)epsilonf) transitions. The dissociation processes of the multiply charged parent ions have also been evaluated from variations of photoelectron-photoion coincidence (PEPICO) and PIPICO spectra with the photon energy. From each Br(3p(3/2)) (189.9 eV) and I(4p(3/2)) threshold (129.9 eV), quintuple ionization of the molecules begins to play important roles in the phototionization, subsequently yielding ion pairs of X3+-X2+ (X=Br, I). From the I(3d(5/2)) threshold (627.3 eV), loss of six electrons from iodine molecule additionally begins to play a minor role in the multiple photoionization, giving rise to the formation of ion pairs of either I3+-I3+ or I4+-I2+. A direct comparison of the strengths and the ranges of the 1(4d) and Br(3d) giant resonances was successfully made from dissociative photoionization of IBr. Over the entire energy range examined, 60 < E < 133 eV, biased charge spread relevant to the specific core-hole states of IBr is observed, presumably reflecting the fact that charge localizes mostly in the excited atoms, which can be accounted for mainly by a two step decay via a fast dissociation followed by autoictnization upon the VUV absorption. (C) 2002 Elsevier Science B.V. All rights reserved.