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Superfluid Helium Droplets: A Uniquely Cold Nanomatrix for Molecules and Molecular Complexes
Author(s) -
Toennies J. Peter,
Vilesov Andrey F.
Publication year - 2004
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.200300611
Subject(s) - helium , superfluid helium 4 , matrix isolation , isothermal process , chemical physics , molecule , nanoscopic scale , liquid helium , superfluidity , chemistry , spectroscopy , phase (matter) , gas phase , ternary operation , nanotechnology , materials science , thermodynamics , physics , organic chemistry , condensed matter physics , quantum mechanics , computer science , programming language
Herein, recent experiments on the spectroscopy and chemical reactions of molecules and complexes embedded in helium droplets are reviewed. In the droplets, a high spectroscopic resolution, which is comparable to the gas phase is achieved, while an isothermal low‐temperature environment is maintained by evaporative cooling at T =0.37 K ( 4 He droplets) or 0.15 K ( 3 He droplets), lower than possible in most solid matrices. Thus the helium‐droplet technique combines the benefits of both the gas phase and the classical matrix‐isolation techniques. Most important, the superfluid helium facilitates binary encounters, and absorbs the released binding energy upon recombination. Thus the droplet can be viewed as an isothermal nanoscopic reactor, which isolates single molecules, clusters, or even a single reactive encounter at ultralow temperatures.