Interdependence of guest radiationless transitions and localized phonon structure: NH and ND(Athinsp;3Pgr;) in rare gas lattices

摘要

Time and wavelength resolved fluorescence techniques are used to study vibrational relation of NH and ND(Athinsp;3Pgr;) substitutional guests in rare gas lattices. Temperature dependent localized phonon spectral structure is analyzed to show that the groundXthinsp;3Sgr;minus;state undergoes near free rotation, while the excitedAthinsp;3Pgr; state librates. The barriers to free rotation inAthinsp;3Pgr; reflect the anisotropy of the attractive, polarizability dependent NHndash;lattice interaction. The vibrational relaxation energy gap law is strongly violated, with NH rates 10ndash;102higher than ND rates. These rates are independent of temperature forTquest;25thinsp;deg;K in Ar, andTquest;37thinsp;deg;K in Kr; however, intersystem crossing byAthinsp;3Pgr; (vprime;=0) in Kr shows a dramatic temperature dependence resulting from stimulated phonon emission. It is proposed that the localized near free rotation mode accepts energy during vibrational relaxation, while delocalized lattice phonon modes accept energy during intersystem crossing. The average accepting frequency in Kr is only quest; (1/2) the host phonon maximum frequency, thus indicating that single accepting frequency theories are only semiquantitatively applicable.