Dynamics of highly excited barium atoms deposited on large argon clusters. I. General trends

Abstract

Ba(Ar)(approximately 750) clusters were generated by associating the supersonic expansion and the pick-up techniques. A femtosecond pump (266.3 nm)-probe (792 or 399.2 nm) experiment was performed to document the dynamics of electronically excited barium within the very multidimensional environment of the argon cluster. Barium was excited in the vicinity of the 6s9p (1)P state and probed by ionization. The velocity imaging technique was used to monitor the energy distribution of photoelectrons and photoions as a function of the delay time between the pump and the probe pulses. A complex dynamics was revealed, which can be interpreted as a sequence/superposition of elementary processes, one of which is the ejection of barium out of the cluster. The latter has an efficiency, which starts increasing 5 ps after the pump pulse, the largest ejection probability being at 10 ps. The ejection process lasts at a very long time, up to 60 ps. A competing process is the partial solvation of barium in low lying electronic states. Both processes are preceded by a complex electronic relaxation, which is not fully unraveled here, the present paper being the first one in a series.

Unsupervised joint Bayesian decomposition of a sequence of photoelectron spectra

“…After 2 ps, this peak has a very low amplitude and a very high width: this is typical of a peak that disappears by vanishing into the background. The estimation confirms quantitatively the qualitative observation of [1] that the energy of one of the electronic levels of the Ba-Ar n system varies in time. This suggests that the corresponding energy level is very sensitive to the argon environment about barium and that barium solvates progressively into the argon cluster.…”

“…This validates the presented label sampling because due to the high value of S, the method proposed in [5] does not provide good results. Also, it appears that the evolutions of the peaks are smoother than the one obtained after a sequential decomposition as it was implemented in [1] (not shown). The estimation points out that one peak is shifting in energy: its energy increases slightly from 1.18 to 1.20 eV between 0 and 0.5 ps, then decreases, and reaches 1.11 eV at 2 ps.…”

“…The distribution of the electrons with respect to their energy is the so-called photoelectron spectrum; it can be modeled as a sum of peaks (which informs on the electronic energy distribution of the system under consideration) superimposed on a continuum [1]. The system considered in section 5 is a single very excited barium atom (Ba) bound to a cluster of several hundreds of argon atoms (Ar).…”

Spectroscopy and Dynamics of K Atoms on Argon Clusters

“…Contrary to Ba 12,21 or Ca 14 on an Ar surface, for which the ejection of the metal atom is a minor process, it occurs systematically for excitation of potassium in this energy range.…”

Joint Bayesian decomposition of a spectroscopic signal sequence with RJMCMC

“…It typically gathers several peaks whose positions and areas give informations about the chemical composition of the sample analysed. Some chemical experiments involve several spectra of the same sample acquired at different instants or temperatures [1], [2]. Thus, data are a sequence of different spectra, although two contiguous spectra (a spectrum and the one acquired at the next or previous instant or temperature) are similar because they gather the same peaks which slowly evolve between them ( Fig.…”