Cavity ring-down spectroscopy and theoretical calculations of the S1(B3u1)←S(Ag1) transition of jet-cooled perylene

Abstract

As part of our long-term program to test the diffuse interstellar band-polycyclic aromatic hydrocarbon hypothesis, we have investigated the S(1)<--S(0) electronic transition of neutral perylene (C(20)H(12)) in a combined experimental and theoretical study. Jet-cooled perylene was prepared with a pulsed discharge slit nozzle and detected by cavity ring-down spectroscopy. A number of vibronic features were observed in the 24 000-24 900 cm(-1) spectral range. Density functional and ab initio calculations were performed to determine the geometries, harmonic vibrational frequencies, and normal coordinates of both the S(0) and S(1) electronic states. A rotational temperature of 52+/-5 K was derived from a rotational contour analysis of the vibronic band associated with the 0-0 transition. A Franck-Condon treatment was carried out to calculate the vibronic spectrum of the S(1)<--S(0) transition. A good agreement was found between the calculated and the experimental spectra. A vibrational assignment is proposed and six normal modes are identified. The contribution of neutral compact polycyclic aromatic hydrocarbons to the diffuse interstellar bands is briefly discussed.

Low-lying excited states in crystalline perylene

“…1 B and C. The fundamental (lowest energy) singlet transition is observed at 2.98 eV in the gas phase (Fig. 1D), with pronounced excited-state vibronic replica found for hυ 1 = 42 meV, hυ 2 = 164 meV, and their linear combinations, respectively (46)(47)(48). The transition dipole moment (TDM) of this lowest singlet excitation [S 1 , highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) transition (49)] is oriented along the long molecular axis (50), as shown in the Inset of Fig.…”

The Titan Haze Simulation experiment on COSmIC: Probing Titan’s atmospheric chemistry at low temperature

“…The exponential decay of the number of photons escaping the cavity (ring down signal) has a characteristic time from which the absolute absorbance associated with the gas present in the cavity can be determined. This diagnostic has been successfully used to investigate the spectral signature of astrophysically relevant neutral and ionized carbon-rich molecules (Biennier et al, 2003(Biennier et al, , 2004Tan and Salama, 2005a, 2005bSalama, 2007Salama, , 2008Salama et al, 2011) produced in the COSmIC plasma expansion. CRDS was not used in this study but is succinctly described here as it is an intrinsic part of the COSmIC/THS setup and will be used in future Titan gas phase experiments on COSmIC/THS.…”

Searching for Naphthalene Cation Absorption in the Interstellar Medium

“…The experimental approach has been described previously (Biennier et al 2003;Tan & Salama 2005, 2006. In brief, a pulsed planar supersonic beam expansion containing the sample (naphthalene) seeded in Ar is prepared with a PDN.…”