Line broadening in electronic spectra of anthracene derivatives inside superfluid helium nanodroplets

  • Electronic spectroscopy of molecules profits greatly from superfluid helium droplets serving as a gentle cryogenic matrix. Characteristic features of electronic spectra in helium droplets are a solvent shift, phonon wings, and in rare cases a splitting of zero phonon lines. For the majority of molecules investigated so far in helium droplets the vibrational fine structure in electronic spectra resembles what was observed in a supersonic jet. The electronic spectra of three methylated anthracene derivatives and one phenylated anthracene discussed in this paper reveal remarkable effects in the vibrational fine structure due to solvation in helium droplets. For all four compounds the vibrational frequencies were almost not affected by the helium environment. However, if the electronic excitation is accompanied by nuclear rearrangement, the spectra showed remarkable line broadening in helium droplets. This is the case for 2-methylanthracene and 9-phenylanthracene. The corresponding line shape was of Lorentzian type and, thus, attributed to damping of the excited system by the helium environment. According to the linewidth the damping time constant was determined to be about 0.3 ps in the case of 2-methylanthracene and 0.1 ps for 9-phenylanthracene.

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Author:Dominik Pentlehner, Ch. Greil, B. Dick, Alkwin Slenczka
Parent Title (English):The Journal of Chemical Physics
Document Type:Contribution to a Periodical
Publication Year:2010
Tag:Anthracene derivates; Electronic spectroscopy; Helium nanodroplets
faculties / departments:Fakultät für Chemische Technologie und Wirtschaft
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 54 Chemie
6 Technik, Medizin, angewandte Wissenschaften / 62 Ingenieurwissenschaften / 620 Ingenieurwissenschaften und zugeordnete Tätigkeiten