Electronic spectroscopy of 9,10-dichloroanthracene inside helium droplets

Abstract

The spectroscopy of molecules doped into superfluid helium droplets provides information on both, the dopant molecule and the helium environment. Electronic spectra of 9,10-dichloroanthracene in helium droplets are presented and compared with corresponding gas phase spectra to unravel the influence of the helium environment. The combined investigation of fluorescence excitation and dispersed emission provides information on dynamic processes in addition to energetic conditions. For vibronic states, the helium induced decay channels dominate over all intramolecular channels that contribute to the gas phase behavior. In addition to the triplet splitting caused by the Cl isotopes, a fine structure resolved for all transitions in the fluorescence excitation spectrum was found, which is the signature of microsolvation of this compound in helium droplets. This fine structure is identified as a single pure molecular transition accompanied by a sharply structured phonon wing. The corresponding fine structure measured for bare anthracene shows remarkable differences.

Microsolvation in superfluid helium droplets studied by the electronic spectra of six porphyrin derivatives and one chlorine compound

“…In contrast to our previous comparative studies which we have done for anthracene derivatives or pyrromethene dye molecules, [3][4][5][6][7] for the porphyrin derivatives the low energy bending or torsional modes of the various substituents are absent in helium droplets. Thus, extended progressions possibly significantly broadened by the interaction with the helium environment were not observed.…”

“…3 As deduced from a systematic investigation including photochemically inactive species, the changing electron density distribution appeared to be a key quantity responsible for the spectral signature of solvation of molecules in helium droplets. [3][4][5][6][7] Besides a solvent shift, which is generally observed with any kind of solvent, one of the first helium-induced features observed in electronic spectra was the double peak splitting of all zero phonon lines (ZPL) of tetracene. 8,9 Much effort has been put into the investigation of the details of this partica) Present address: Zeiss Laser Optics GmbH, Oberkochen, Germany.…”

Microsolvation of molecules in superfluid helium nanodroplets revealed by means of electronic spectroscopy

“…Much information on helium induced line broadening was provided by systematic investigations of a series of related dopant species. For three molecular species namely Pyrromethene (Pentlehner et al, 2011; Stromeck-Faderl et al, 2011), Porphyrin (Pentlehner et al, 2011; Riechers et al, 2013), and Anthracene (Pentlehner et al, 2010, 2011; Pentlehner and Slenczka, 2012, 2013) several derivatives have been investigated which differ in the number and the species of substituents such as methyl, ethyl, propyl, phenyl, and cyano groups which substitute hydrogen atoms in the periphery of the molecular compound. The main conclusions concerning the influence of electronic and vibrational degrees of freedom will be outlined for each of the three molecular species.…”

“…According to this mechanism, the change of the electron density distribution is the driving force for intra- and intermolecular rearrangements which become effective on the line widths in the electronic spectra of these two Anthracene derivatives. Further details of these spectra are discussed in Pentlehner et al (2010, 2011); Pentlehner and Slenczka (2012, 2013). Thus, the systematic investigation of Anthracene derivatives provides evidence for the change of the electron density distribution being responsible for helium induced spectral features.…”

Helium induced fine structure in the electronic spectra of anthracene derivatives doped into superfluid helium nanodroplets

“…Consequently, a systematic study of, for example, a series of derivatives of a spectroscopically well understood molecule may help to interpret the helium induced spectral features and, thereby, to learn more about microsolvation in superfluid helium droplets. Motivated by this idea, the present paper is part of an extended investigation of anthracene derivatives 10,11,22,23 which was preceded by similar studies on pyrromethene dye molecules 24 as well as porphyrin derivatives. 25 The present paper reports on electronic spectroscopy of 9-cyanoanthracene (9-CNA) and 9-chloroanthracene (9-CA) doped into superfluid helium droplets and complements our investigation of a series of anthracene derivatives.…”