Spectroscopy and dynamics in helium nanodroplets

Abstract

Abstract. This article provides a review of recent work in the field of helium nanodroplet spectroscopy with emphasis on the dynamical aspects of the interactions between molecules in helium as well as their interaction with this unique quantum solvent. Emphasis is placed on experimental methods and studies introducing recent new approaches, in particular including time-resolved techniques. Corresponding theoretical results on the energetics and dynamics of helium droplets are also discussed.

Surface Deposition and Imaging of Large Ag Clusters Formed in He Droplets

“…Helium nanodroplets with an average size of <N He > = 4·10 7 and 2. The average number of Ag atoms captured per He droplet, <N Ag >, has been estimated using the attenuation of the He droplet beam, as described in detail elsewhere 14 .…”

“…Successful coupling of the He droplet technique with laser spectroscopy in the infrared and visible spectral regions in the study of the structure and dynamics of small molecular and atomic clusters in He droplets is reviewed in Refs. [1][2][3][6][7] .…”

A new sensitive detection scheme for helium nanodroplet isolation spectroscopy: application to benzene

“…[1][2][3][4] The low temperature of the helium droplets and the weak interactions of the helium with the solutes allows for the observation of greatly simplified spectra. None of the spectroscopic methods used in helium nanodroplet isolation spectroscopy records directly the absorption spectrum.…”

“…[5][6][7][8][9] Whereas these two techniques use direct probes of the molecular absorption, almost all other techniques rely on the non-radiative energy transfer from the optically excited molecule to the helium environment. [1][2][3][4] Following this energy transfer, the heated helium droplets cool down to their equilibrium temperature of 0.38 K by the evaporation of helium atoms from their surface, thereby reducing their size. This reduction in droplet size can be readily detected using mass spectrometry, since the cross section for electron impact ionization of droplets consisting of hundreds or more helium atoms scales with the geometrical cross section, i.e.…”

Absorption spectroscopy of adenine, 9-methyladenine, and 2-aminopurine in helium nanodroplets

“…Helium nanodroplets have emerged in recent years as an almost ideal matrix to reach those goals. [35][36][37][38] Single molecules can be embedded into these droplets and the ultra-low temperature of the droplets (0.38 K) enables studies at considerably lower internal temperatures of the molecules than possible with molecular beam techniques. In particular for medium-to large-sized molecules, this lower internal temperature has been found to be crucial to obtain well-resolved spectra.…”