Characterization of laser ablation as a means for doping helium nanodroplets

Abstract

Universal molecule injector in liquid helium: Pulsed cryogenic doped helium droplet source Rev. Sci. Instrum. 73, 3606 (2002);

Superfluid Helium Droplets: A Uniquely Cold Nanomatrix for Molecules and Molecular Complexes

“…[110] Laser ablation of Mg close to the continuous helium droplet source, was used to form helium droplets doped with Mg atoms and Mg + ions. [143] The pick-up process leads to a decrease in the initial droplet size, a result of the kinetic energy and the internal energy of the impacting molecule, as well as its chemical potential, all of which are transferred to the droplet and lead to a subsequent rapid evaporation of He atoms. As a rule of thumb 1 eV of heat released corresponds to the evaporation of about 1600 4 He atoms or 4300 3 He atoms from the droplets.…”

Density functional theory of doped superfluid liquid helium and nanodroplets

“…Development of new techniques for doping helium droplets with charged impurities allow the controlled study of positive ions in superfluid helium. 192 While neutral species could be excited in helium droplets by a resonant laser and detected essentially against a zero background, similar experiments have had limited success for ions. It is only recently that experimentalists have found a way to study the dynamics of photoexcited ions in helium droplets.…”

Photoionisaton of pure and doped helium nanodroplets

“…This applies to direct one-photon PI of dopant atoms [58,117], to non-resonant PI using ultrashort laser pulses, to REMPI of dopant atoms, whose intermediate excited states are non-desorbing [59,82,83,118], and to resonant REMPI of molecular dopants into the vibronic ground states of their cations [119]. Note that ion-doped He droplets have also been observed when doping He droplets with preformed ions, e. g. using laser ablation or ion traps [40,41,120]. However, due to the technical difficulty in detecting these massive ions with high sensitivity, they have only rarely been used as a quantitative observable.…”

“…Laser evaporation has been established as an alternative way to produce doped He droplets by the authors [40,41]. The material is ablated from a rotating and translating rod by a pulsed infrared, visible or ultraviolet laser.…”