On the possibility of selecting molecules embedded in superfluid helium nanodroplets (clusters)
Institute of Spectroscopy, Russian Academy of Sciences, ul. Fizicheskaya 5, Troitsk, Moscow, 108840, Russian Federation
Methods for producing beams of nanometer-sized
superfluid helium droplets and techniques for embedding single
molecules and clusters in them open up many possibilities for
spectroscopy, as well as providing insight into many physical
and chemical processes occurring on the atomic and molecular
level at extremely low temperatures (T ≤ 0.4 K). In this paper, results of investigations into the possibility of selecting molecules embedded in superfluid helium nanodroplets (clusters) are reviewed. The method proposed starts with the selective vibrational excitation of cluster-embedded molecules by intense IR laser radiation (which greatly reduces the size of the excited clusters), followed by size-separating the clusters via scattering the cluster beam from a crossing molecular (atomic) beam. It is shown that molecules of a particular isotope (component) composition can be selected with this method. The advantages and disadvantages of the method are discussed. Methods for creating and doping helium nanodroplets and some other examples of their applications are also outlined.