title: Estimation of the fluorescence lifetime for optically inaccessible exciplexes in nonpolar solutions under ionizing irradiation.
abstract: X-irradiation of nonpolar solutions likely provides a possibility to create exciplexes for any donor-acceptor pair that would energetically and sterically allow this. Thorough study and characterization of X-radiation generated exciplexes usually cannot be carried out with conventional methods because of the complex and non-exponential formation and decay dynamics of these species. In this paper, we present a simple and universal experimental approach for the estimation of fluorescence lifetimes (τF) of X-radiation generated exciplexes. The suggested procedure is based on the comparison of quenching of the exciplex emission band and the emission band from a standard luminophore with a known excited state lifetime by dissolved oxygen. Using this approach we report the τF values for two systems with optically inaccessible exciplexes, diphenylacetylene-N,N-dimethylaniline (DMA) and p-terphenyl-DMA, and for two typical exciplex forming systems, naphthalene-DMA and anthracene-DMA. All the found τF values for the X-radiation generated exciplexes lie in the range of 50-70 ns. The accuracy of this approach was checked by time-resolved measurements under X- or near-UV irradiation for those pairs, whose properties make this feasible. The proposed method gives a possibility to avoid a complex numerical evaluation of the non-exponential kinetics of recombination luminescence, and can be used to estimate the characteristic τF values for luminophores and excited complexes formed under X-radiation.
authors.affiliation: Institute of Chemical Kinetics and Combustion SB RAS, 3, Institutskaya Str., 630090 Novosibirsk, Russian Federation. melnikov@kinetics.nsc.ru.
authors.forename: Anatoly R
authors.initials: AR
authors.lastname: Melnikov
authors.forename: Evgeny V
authors.initials: EV
authors.lastname: Kalneus
authors.forename: Valeri V
authors.initials: VV
authors.lastname: Korolev
authors.forename: Peter S
authors.initials: PS
authors.lastname: Sherin
authors.forename: Vsevolod I
authors.initials: VI
authors.lastname: Borovkov
authors.forename: Dmitri V
authors.initials: DV
authors.lastname: Stass
mesh_terms: D000114:Acetylene / Q000031:analogs & derivatives / Q000737:chemistry; D000473:Alkanes / Q000737:chemistry; D000814:Aniline Compounds / Q000737:chemistry*; D000873:Anthracenes / Q000737:chemistry; D005453:Fluorescence; D007700:Kinetics; D009281:Naphthalenes / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D055668:Photochemical Processes; D012996:Solutions / Q000737:chemistry / Q000528:radiation effects; D013730:Terphenyl Compounds / Q000737:chemistry; D014965:X-Rays
chemical_list: D000473:Alkanes; D000814:Aniline Compounds; D000873:Anthracenes; D009281:Naphthalenes; D012996:Solutions; D013730:Terphenyl Compounds; C007548:n-dodecane; C031721:naphthalene; C044735:biphenylacetylene; C034020:anthracene; D000114:Acetylene; D010100:Oxygen