Suppression of multiphoton ionization of aniline in large superfluid helium droplets

Electron Diffraction of Ionic Argon Nanoclusters Embedded in Superfluid Helium Droplets

“…The arrival times of the doped droplets are also indicative of their sizes. Although consistent with our previous observation, 52,55,56 two groups of droplets coexist even at source temperatures of 16 and 18 K, and they are not well separated in arrival time in the diffraction region, particularly when the response time of the detector is 200 μs. The small shoulder leading to the main peak in the dot-dashed line represents the small size group: its intensity is further reduced by the ionization grid and overfocusing by the Einzel lens.…”

“…Figure shows the radial profiles of the experimental diffraction pattern of ionized small Ar clusters obtained after 1 619 653 shots (90 h of total experiment time). The exposure time of each pulse is 40 μs, and the total exposure time is 64.8 s. The droplet source temperature was at 18 K, with an average droplet size of 6 × 10 4 helium atoms (only the larger group survives and is used in this experiment, see text above on the experimental setup). ,, After passing through a region of argon gas with a distance of 1 cm and a doping pressure of 4 × 10 –5 Torr, the most probable Ar N is with N = 3, but Ar 2 and Ar 4 are also probable. Based on the doping statistics, the fitting equation thus includes contributions from monomers to tetramers of ionized argon: The structures of Ar N + are obtained from the literature, and the diffraction profiles of monomers to tetramers are represented by I 1 to I 4 .…”

Electron diffraction as a structure tool for charged and neutral nanoclusters formed in superfluid helium droplets

“…In fact, our experimental characterization of droplets produced from different types of pulse valves has repeatedly confirmed the bimodal distribution of droplet sizes. 60–63 On the other hand, the ionization and detection scheme can be easily implemented in most laboratories, and hence this knowledge on the conditions of the droplets can be obtained with minimal efforts.…”

Helium Droplet Mass Spectrometry

“…In two subsequent studies, Alghamdi and co-workers investigated EI and MPI of large HNDs (N ~10 8 ) doped with aniline. The authors found that in both cases, the large HND environment suppressed the ionization mechanism via shielding of the neutral dopant against charge transfer from He 2 + [194] and caging of photoelectrons allowing for recombination with photoionic (fragments) [195], respectively. A recent study demonstrated the feasibility of electron diffraction of smaller HNDs (N = 800-1.4×10 5 ) doped with CS 2 [196].…”