title: Fine structure of the (S(1)<--S(0)) band origins of phthalocyanine molecules in helium droplets.
abstract: The laser-induced fluorescence (LIF) excitation spectra of free base phthalocyanine (Pc), Mg-Pc, and Zn-Pc molecules in superfluid helium droplets at T=0.38 K have been studied. The spectra reveal the rich vibronic structure of the S(1)<--S(0) electronic transitions. The band origins of the transitions consist of zero phonon lines accompanied by phonon wings, which originate from simultaneous electronic excitation of the molecule and excitation of the collective modes of the helium surrounding it. The phonon wings have discrete structures suggesting localization of some helium atoms in the neighborhood of the molecules. Zero phonon lines of Mg-Pc and Zn-Pc molecules are split into three components, which are separated by 0.2-0.4 cm(-1). Possible mechanism of splitting involves static or dynamic Jahn-Teller interaction of metal-phthalocyanine molecules in the twofold degenerate S(1)((1)E(u)) state with the helium shell.
authors.affiliation: Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Lehnig
authors.forename: Mikhail
authors.initials: M
authors.lastname: Slipchenko
authors.forename: Susumu
authors.initials: S
authors.lastname: Kuma
authors.forename: Takamasa
authors.initials: T
authors.lastname: Momose
authors.forename: Boris
authors.initials: B
authors.lastname: Sartakov
authors.forename: Andrey
authors.initials: A
authors.lastname: Vilesov