Two-photon excitation spectra of the lowest electronic states of 2,2\’-bipyridine

Year: 1982

Authors: Castellucci E., Salvi P.R., Foggi P.

Autors Affiliation: Istituto di Chimica Fisica, Universitá di Firenze, 50121 Firenze, Italy

Abstract: The two-photon absorption spectra of 2,2\’-bipyridine single crystal at 77 K and solution Li the region 30000-38500 cm-1 and 32000-38500 cm-1, respectively, have been measured. The lowest (n,p*) and (p,p*) electronic systems have been observed and discussed in terms of two-photon allowed and vibronicauy induced transitions. Proportionality factors for two-photon intensities in the crystal were calculated in the oriented gas model approximation and used to assign the observed bands to the proper tensor under the C2h molecular symmetry. In the (n, p*) absorption region of the crystal the (0-0) 1Bg(n,p*) ? 1Ag, not active in one-photon experiments, has been found at ˜30075 cm-1. The 1Bg(n, p*) -1Au(n, p*) energy gap amounts to ?800 cm-1. The observed vibronic structure is assigned to totally symmetric vibrational modes through a Franck-Condon mechanism. The (p, p*) absorption region is discussed on the basis of both the crystal and solution spectrum. McClain\’s polarization rules for the solution and polarized crystal intensities show that the (p, p*) two-photon absorption region begins at ˜34300 cm-1. Transitions to Bu × bu × ag states are responsible of the band pattern up to about 37000 cm-1 The relative two-photon cross section of 2.2\’-bipyridine in solution at 34780 cm-1 has been estimated to be of the order of 6 × 10-2 that of benzend\’s 1B2u × b2u (?14). The one-photon absorption spectrum of the solution reran here has revealed a shoulder on the red of the well-known maximum at {all equal to}2835 A and it has been assigned to the (0-0)1 Bu(p, p*).

Journal/Review: CHEMICAL PHYSICS

Volume: 66 (3)      Pages from: 281  to: 291

KeyWords: pyrene
DOI: 10.1016/0301-0104(82)88027-0

Citations: 6
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