FEMTOSECOND DISSOCIATION OF CORE-EXCITED HCL MONITORED BY FREQUENCY DETUNING

Core excitation of gaseous HCl to the dissociative sigma state leads to a deexcitation spectrum with two qualitatively different contributi ons-a broad molecular background and narrow atomic lines. The experime nt demonstrates that the ratio of integrated intensities from these tw o contributions depends crucially on the excitation frequency; the mol ecular background is enhanced with increased detuning of the photon fr equency. This is discussed in a time-dependent model, using the concep t of an effective duration time for the resonant x-ray scattering proc ess. [S0031-9007(97)04296-8].