N. Nijegorodov et al., Evolution of absorption, fluorescence, laser and chemical properties in the series of compounds perylene, benzo(ghi)perylene and coronene, SPECT ACT A, 57(13), 2001, pp. 2673-2685
Citations number
42
Categorie Soggetti
Spectroscopy /Instrumentation/Analytical Sciences
Journal title
SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
Absorption, fluorescence and laser properties of perylene, benzo(ghi)peryle
ne and coronene are studied experimentally (under the same conditions) and
quantum chemically at room (293 K) and at low (77 and 4 K) temperatures and
direct comparison is made between the results for each molecule. All the m
ain absorption and fluorescence parameters such as oscillator strength, f(e
), quantum yield, gamma, decay time, tau (f), fluorescence rate constant, k
(f) (Einstein coefficient, A) and intersystem crossing rate constant, k(ST)
. are measured or calculated. The systems of singlet and triplet levels for
these compounds are simulated and analyzed. Triplet states mixing with the
lowest singlet S-1 state are determined. The low values of k(ST) found are
explained. The possible vibronic coupling in the molecule coronene is disc
ussed. The nature of the three fluorescence bands of coronene observed is i
nterpreted. The change in the arrangement of the singlet and triplet levels
of the studied compounds is interpreted quantum-chemically. It is found th
at at room temperature (293 K), only perylene shows laser action, while all
three compounds show good laser oscillation at low temperature ( < 100 K).
The differences in the laser properties of these compounds are explained b
y the inversion of the S-p(L-1(a)) and S-alpha(L-1(b)) levels which occurs
in the transition from perylene to benzo(ghi)perylene. Chemical properties
of the compounds studied are outlined. Linear and quasi-linear fluorescence
spectra of perylene and benzo(ghi)perylene. obtained at 77 and 4 K. can be
used in the identification of these compounds. (C) 2001 Elsevier Science B
.V. All rights reserved.