title: Electronic spectroscopy of 1-(phenylethynyl)naphthalene.
abstract: Recently 1-(phenylethynyl)naphthalene (1-PEN) was suggested to be the primary dimerization product of phenylpropargyl radicals and therefore an important polycyclic hydrocarbon in combustion processes. Here we describe a spectroscopic investigation of a genuine 1-PEN sample by several complementary techniques, infrared spectroscopy, multiphoton ionization (MPI), and threshold photoelectron spectroscopy. The infrared spectrum recorded in a gas cell confirms that 1-PEN is indeed the previously observed dimerization product of phenylpropargyl. The origin of the transition into the electronically excited S1 state lies at 30823 cm(-1), as found by MPI. Considerable vibrational activity is observed, and a number of low-wavenumber bands are assigned to a progression in the torsional motion. Values of 6 cm(-1) (S0) and 17 cm(-1) (S1) were derived for the fundamental of the torsion. In the investigated energy range the excited state lifetimes are in the nanosecond range. Spectra of the 1-PEN/Ar cluster exhibit a red shift of the electronic origin of 22 cm(-1), in good agreement with other aromatic molecules. A threshold photoelectron spectrum recorded using synchrotron radiation yields an ionization energy of 7.58 eV for 1-PEN. An excited electronic state of the cation is found at 7.76 eV, and dissociative photoionization does not set in below 15 eV.
authors.affiliation: Institute of Physical and Theoretical Chemistry, University of Würzburg , Am Hubland, D-97074 Würzburg, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Constantinidis
authors.forename: Melanie
authors.initials: M
authors.lastname: Lang
authors.forename: Jörg
authors.initials: J
authors.lastname: Herterich
authors.forename: Ingo
authors.initials: I
authors.lastname: Fischer
authors.forename: Johannes
authors.initials: J
authors.lastname: Auerswald
authors.forename: Anke
authors.initials: A
authors.lastname: Krueger