title: Low-temperature photoluminescence of p-nitroaniline and o-methyl-p-nitroaniline crystals.
abstract: Photoemission spectra of para-nitroaniline (p-NA) and ortho-methyl-para-nitroaniline (MNA) single crystals measured between 5 and 250K revealed that the MNA crystals emit phosphorescence and fluorescence in contrast with the p-NA crystals which have only fluorescence. It is assumed that the fluorescence of p-NA crystals at 5K originates from the doublet state of negatively charged polarons while the fluorescence of MNA crystals at 60K is due to trap states. The Stokes shift between absorption and emission onsets, measured at 5K, is much larger in the p-NA crystals than in the MNA and meta-nitroaniline (m-NA) crystals. This fact is rationalized by different geometrical changes caused by excitation.
authors.affiliation: Institute of Physical and Theoretical Chemistry, Wrocław University of Technology, Wybrzeze Wyspiańskiego 27, 50-370 Wrocław, Poland. magdalena.m.szostak@pwr.wroc.pl
authors.forename: M Magdalena
authors.initials: MM
authors.lastname: Szostak
authors.forename: Bolesław
authors.initials: B
authors.lastname: Kozankiewicz
authors.forename: Józef
authors.initials: J
authors.lastname: Lipiński
mesh_terms: D000042:Absorption; D000814:Aniline Compounds / Q000737:chemistry*; D003080:Cold Temperature; D003460:Crystallization; D049449:Luminescence; D013816:Thermodynamics
chemical_list: D000814:Aniline Compounds; C522990:o-methyl-p-nitroaniline; C008625:nitroaniline