Wave packet dynamics of K₂attached to helium nanodroplets

Abstract

The dynamics of vibrational wave packets excited in K2 dimers attached to superfluid helium nanodroplets is investigated by means of femtosecond pump–probe spectroscopy. The employed resonant three-photon-ionization scheme is studied in a wide wavelength range and different pathways leading to K2+ formation are identified. While the wave packet dynamics of the electronic ground state is not influenced by the helium environment, perturbations of the electronically excited states are observed. The latter reveal a strong time dependence on the timescale 3–8 ps which directly reflects the dynamics of desorption of K2 off the helium droplets.

Wave Packet Dynamics in Triplet States of Na2 Attached to Helium Nanodroplets

“…12. The time range 0-600 fs is omitted because the signal 6 is entirely masked by the autocorrelation trace of the copropagating pump and probe pulses.…”

“…Due to the difficulty of implanting impurities into liquid helium, no real-time measurements with molecules in bulk liquid or solid helium have been reported until now. In a recent publication from our group, we presented for the first time pump-probe spectroscopy of covalently bound K 2 dimers attached to superfluid helium nanodroplets 12 . Different photoionization schemes were applied to study the influence of the helium environment on the wave packet propagation.…”

“…Upon electronic excitation, alkali atoms and molecules mostly desorb from the droplets as a consequence of evaporation of helium atoms after energy deposition in the helium droplet. The dynamics of the desorption process has been observed for the first time by analyzing the wave packet motion of K 2 dimers on helium droplets 12 .…”

Vibrational relaxation and dephasing of Rb2 attached to helium nanodroplets

“…Besides, the measurement of beam depletion using a separate detector was interpreted as clear evidence that excited Rb 2 molecules desorb off the droplets on the time scale of the flight time from the laser interaction region to the detector (∼ 1 ms). Furthermore, earlier measurements with K 2 dimers as well as theoretical simulations on K atoms attached to helium nanodroplets indicated desorption times in ranging 3 -8 ps and 10 -30 ps, respectively [18,26].…”

“…The vibrational wave packet dynamics of alkali metal dimers attached to helium nanodroplets has been studied using the femtosecond pump-probe technique in a series of experiments in our group [3,[18][19][20]. Alkali metal atoms and molecules represent a particular class of dopant particles due to their extremely weak binding to the surface of He droplets in bubble-like structures [21][22][23][24].…”