title: Single- and two-photon excited fluorescence in organic nonlinear optical single crystal 3-(1,1-dicyanoethenyl)-1-phenyl-4,5-dihydro-1H-pyrazole.
abstract: Fluorescence of nonlinear optical organic single crystal of 3-(1,1-dicyanoethenyl)-1-phenyl-4,5-dihydro-1H-pyrazole (DCNP) excited by a nonabsorbed light pulses from Q-switched Nd:YAG laser λ = 1064 nm as well as absorbed λ = 532 nm light is reported. Two mechanisms of two-photon excited fluorescence are considered: (i) direct two-photon excited fluorescence and (ii) single-photon excitation due to reabsorption of light generated in process of second harmonic generation (SHG) by the crystal due to its nonlinear optical properties. Strong anisotropy of fluorescence that has been observed is linked with uniaxial molecular alignment. Fluorescence decay profile shows two- exponential decay with lifetimes of emitting species of 3.7 and 5.6 ns at 293 K. The excitation and fluorescence spectra of the DCNP single crystal have been measured at 294 K and in function of temperature down to 77.4 K. The strong bathochromic shift of fluorescence spectrum in crystal with respect to fluorescence of DCNP molecule in solution is observed and interpreted with possible formation of molecular aggregates.
authors.affiliation: Institute of Physical and Theoretical Chemistry, Department of Chemistry, Wybrzeze Wyspianskiego 27, Wroclaw University of Technology, 50-370 Wroclaw, Poland. andrzej.miniewicz@pwr.wroc.pl
authors.forename: Andrzej
authors.initials: A
authors.lastname: Miniewicz
authors.forename: Krystyna
authors.initials: K
authors.lastname: Palewska
authors.forename: Lech
authors.initials: L
authors.lastname: Sznitko
authors.forename: Jozef
authors.initials: J
authors.lastname: Lipinski
mesh_terms: D016880:Anisotropy; D005453:Fluorescence; D008958:Models, Molecular; D017785:Photons; D011720:Pyrazoles / Q000737:chemistry*
chemical_list: D011720:Pyrazoles