title: Laser induced fluorescence of Mg-phthalocyanine in He droplets: evidence for fluxionality of large H2 clusters at 0.38 K.
abstract: The formation of Ar and H2 clusters, having up to 900 particles in helium droplets, has been studied via laser induced fluorescence of attached Mg-phthalocyanine (Mg-Pc) molecules. In the experiments, one Mg-Pc molecule in average was added to each He droplet either before or after the cluster species, and the shift of the spectrum of the Mg-Pc molecules was studied as a function of the cluster size. For Ar clusters, about a factor of 2 smaller matrix shift was observed for the late pickup of the Mg-Pc molecules as compared with the prior pickup, indicating that in the former case, the Mg-Pc molecules reside on the surface of the preformed Ar clusters. On the other hand, the spectra of the Mg-Pc molecules attached to H2 clusters are independent of the pickup order, which is consistent with Mg-Pc molecules residing near the center of the H2 clusters in both cases. Therefore H2 clusters remain fluxional in helium droplets at T=0.38 K. No significant differences in the spectra were observed between the para-H2 and ortho-H2 clusters.
authors: Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
authors: Susumu
authors: S
authors: Kuma
authors: Haruka
authors: H
authors: Goto
authors: Mikhail N
authors: MN
authors: Slipchenko
authors: Andrey F
authors: AF
authors: Vilesov
authors: Alexander
authors: A
authors: Khramov
authors: Takamasa
authors: T
authors: Momose