title: Polarized normal-incidence cavity ring-down spectroscopy: probing spiropyran photochromism in thin PMMA films and toluene.
abstract: A normal-incidence geometry, polarization-resolved cavity ring-down spectroscopy technique (polarized NICRDS) is described to probe the polarized absorbance of surface-adsorbed thin films and short-path length liquid samples. The technique is demonstrated by a kinetic study of the photochromic behavior of the spiropyran dye 6,8-dibromo-1', 3'-dihydro-1', 3', 3'-trimethylspiro[2H-1-benzopyran-2, 2'-(2H)-indole]. The technique is shown potentially to have monolayer coverage sensitivity and can measure the angular orientation distribution of analyte molecules. The photochromic kinetics of 6,8-dibromoBIPS in toluene solution were qualitatively consistent with a previous study of this molecule using conventional absorption spectroscopy. The absorption polarizations and slow ring-closing kinetics measured in a thin poly(methyl methacrylate) film are consistent with a strong interaction of the spiropyran and merocyanine forms with the polymer matrix.
authors.affiliation: Department of Chemistry, University of Nevada, Reno, Nevada 89557-0216, USA.
authors.forename: Jordan H
authors.initials: JH
authors.lastname: Mantha
authors.forename: Ali I
authors.initials: AI
authors.lastname: Ismail
authors.forename: Joseph I
authors.initials: JI
authors.lastname: Cline