Spectroscopy of F2 in Ne matrices

Abstract

The excited states of free and matrix-isolated F 2 were investigated in the windowless VUV region by absorption and excitation spectroscopy. In emission the f 3 ⌸ g →a 3 ⌸ u laser band of F 2 at 7.72 eV with a radiative lifetime of 2 ns and a weaker and broader band at 7.47 eV attributed to emission of F 2 aggregates are observed in an Ne matrix independent on excitation energy. The Franck-Condon envelope of the charge transfer state C 1 ⌺ u ϩ extends further to the blue by more than 1 eV in Ne ͑12 to 14 eV͒ compared to the gas phase due to a blueshift of the avoided crossing with the Rydberg 3p u ( 1 ⌺ u ϩ ) state. The H 1 ⌸ u Rydberg state remains unperturbed in the Ne matrix but is blueshifted by 1.24 eV and significantly broadened due to electron-phonon coupling. A previously unreported broad absorption is observed both in the gas phase and in the matrix around 15 eV and is assigned to a strongly perturbed charge transfer state with ⌺ symmetry corresponding to F ϩ *͑ 1 S͒ and F Ϫ ͑ 1 S͒ ions in the dissociation limit. This charge transfer state is strongly perturbed in the gas phase by the high density of np u ( 1 ⌺ u ϩ ) Rydberg states ͑nу4͒ while in Ne matrix it is mixed mainly with the low-lying 4p u ( 1 ⌺ u ϩ ) state. The analogy of the resulting two separated groups of bands with irregular vibrational progressions to the Cl 2 case is shown. Further np u and np u Rydberg progressions and the repulsive 3 ⌺ u ϩ valence state are treated. The utility of matrix-isolated F 2 for a solid state laser is discussed.

Penetration depth of photomobilized F atoms in Ar layers from a sandwich experiment

“…The strength of this spin forbidden transition is perhaps increased compared to the gas phase by an increased mixing with the C 1 ⌺ u ϩ state, which is red shifted in Ne matrices. 22 No fluorescence is observed for excitation into these bands in contrast to the transition to bound states 22 that supports once more the assignment to a repulsive state and indicates that nonradiative transitions to lower lying bound states are negligible. Thus, F 2 is dissociated by 10.15 eV in the photomobility experiments, and subtracting the ground state binding energy of 1.61 eV 25 leads to an excess energy of 8.5 eV that can be distributed to the two F atoms.…”

“…The cross sections in these maxima are at least one order of magnitude smaller compared to those transitions to bound states of F 2 occurring at energies above 12 eV, as treated in detail in Ref. 22. In Ne the band is situated near the red wing of the C 1 ⌺ u ϩ absorption and in Ar just below the nϭ1 and nЈϭ1 matrix excitons.…”

“…3 The emission energies of Rg 2 F trimers, formed with different rare gas atoms Rg, reflect the ionization energies of the rare gas atoms since charge transfer states are involved. 3,27 The variation of emission energies was used to distinguish between F atoms with different local environments, i.e., placed in different layers of the stack. This is illustrated in Fig.…”

“…Excitation of an Ar film, exclusively doped with F 2 , in the Ar exciton band ͑11.8 eV͒ leads to one emission band ͓Fig. 3͑a͔͒ at 315 nm, which is characteristic for Ar 2 F. 15,27 The same excitation energy, combined with an Ar film multiply doped with Kr and F 2 , leads to a complete quenching of the Ar 2 F emission and the appearance of two new bands at 345 and 439 nm ͓Fig. 3͑b͔͒, which have been attributed to ArKrF and Kr 2 F trimers.…”

Rydberg and charge transfer states of F atoms in neon matrices

“…The VUV spectroscopy and photodissociation dynamics of F 2 in neon matrices will be discussed in a forthcoming paper. 14 The inherent simplicity of the rare gas solid-halogen dopant interaction makes this system a paradigm of condensed phase photochemical processes. Molecular dynamics simulations of the photodissociation of F 2 ͑Refs.…”