Vibrational and electronic spectra of matrix-isolated tetracene cations

Electronic absorption spectroscopy of polycyclic aromatic hydrocarbons (PAHs) radical cations generated in oleum: A superacid medium

“…It is characterized by a broad band at about 645 nm and a shoulder at 825 nm. The radical cation of a hexa-alkylated hexabenzocoronene in an isolated matrix [33] shows a strong and broad absorption band at 555 nm followed by another broad band at 840 nm in reasonable agreement with our results. Theoretical calculations [32] also predict for the hexabenzocoronene radical cation a broad band at 450-470 nm and another peak at 750-800 nm.…”

“…There are no doubts about the successful formation of the radical cation of both tetracene and pentacene in oleum as clearly suggested by the strong absorption bands in the visible located respectively at 652.8 and at 760.4 nm. In matrix isolated conditions at 77 K tetracene radical cation gives the following optical transitions: 868, 745, 392 and 348 nm [33]; such transitions are in good agreement with those expected from the I p = (I pn − I p1 ) values, i.e. the differences between the nth ionization potential and the first ionization potential.…”

The low-lying excited states of neutral polyacenes and their radical cations: a quantum chemical study employing the algebraic diagrammatic construction scheme of second order

“…However, the weight of the corresponding determinant in the wavefunctions is almost constant for all polyacene radical cations with 0.87 from naphthalene to 0.82 for hexacene. Since the excitation energy of the B 3u transition decreases with increasing system size, it becomes the lowest excited state for tetracene at ADC(2) level, in agreement with the experimental data [75,77,78]. Since the B 3u transition is ungerade, it is one-photon allowed and thus exhibits substantial oscillator strength increasing from naphthalene with values of 0.084 and 0.058 at the theoretical levels of ADC(2)-s and ADC(2)-x, respectively, to 0.301 and 0.148 for pentacene, for example.…”

Variations in the Peak Position of the 6.2 μm Interstellar Emission Feature: A Tracer of N in the Interstellar Polycyclic Aromatic Hydrocarbon Population

“…Based on more than a decade of laboratory measurements and theoretical calculations (e.g., Hudgins et al 2000;Vala et al 1994;Szczepanski et al 1995;Bauschlicher & Langhoff 1997;Kim & Saykally 2002;Mattioda et al 2003;Oomens et al 2003 and references therein), it is now widely recognized that models based on the composite spectra of PAHs and PAH cations can accommodate the general pattern of band positions, intensities, and profiles observed in the interstellar IR emission spectra as well as the variations in those characteristics (e.g., Langhoff 1996;Allamandola et al 1999;Verstraete et al 2001;Bakes et al 2001Pech et al 2002). Overall, that work indicates that the interstellar 3.3 m band and, to a lesser extent, the 11.2 m band are dominated by the emission of neutral PAHs, whose most prominent bands fall in these regions.…”