No abstract

No abstract

The double-excitation 'I" Rydberg series of He, converging to the N=4 to 9 thresholds, were studied by high-resolution photoionization using synchrotron radiation. Both the principal series with correlation quantum numbers K=N -2 and the secondary series with K=N -4 could be resolved up to previously unobtained n values. This allows a substantially improved analysis of the series with respect to energies and linewidths, leading to an improved understanding of the interseries interferences. The data are in excellent agreement with calculations based on the complex-rotation method.PACS number(s): 32.70.Fw, 32.80.t, 31.50.+w, 31.25.Jf

Inner-shell soft-x-ray absorption of formaldehyde, H2CO, in the region of the C E and 0 K absorption thresholds was studied with high energy resolution using synchrotron radiation from the SX700/II monochromator at BESSY. The absorption spectra were recorded via the total photocurrent yield. The C 1sexcitation spectrum is characterized by a dominant C 1s ' n. resonance and weaker transitions into Rydberg states, each exhibiting vibrational fine structure that is quantitatively analyzed in terms of the normal vibrational modes of H&CO. Isotopic effects on the vibrational modes were studied by taking analogous spectra of D&CO. A Franck-Condon analysis of the vibrationally split spectra yields equilibrium distances, molecular bond angles, and vibrational frequencies of C ls -excited formaldehyde, which show strong isotopic effects. In addition, the ground vibrational level of the lowest Rydberg state (C 1s 3s-a& ) exhibits a pronounced shift to higher excitation energies upon replacement of H by D.This shift, as well as a considerable isotope-dependent line broadening, are presumably caused by perturbations of this state by valence orbitals. Analogous isotopic effects were observed for the 0 1s 3s-a, Rydberg state.PACS number(s): 33.20. Rm, 33.70.w, 33.80.Rv, 35.20.i

No abstract