title: One- and two-photon absorption of a spiropyran-merocyanine system: experimental and theoretical studies.
abstract: We report on the nonlinear optical properties measurements and quantum-chemical calculations of a well-known photochromic system consisting of spiropyran and the merocyanine photoproduct. The study of nonlinear absorption and refraction properties of the molecules dissolved in chloroform were performed with the Z-scan technique, using femtosecond pulses in a wide range of wavelengths. Maxima in the two-photon absorption spectrum at 700 and 1050 nm were found for the merocyanine form, and the corresponding two-photon absorption cross section is 80 GM and 20 GM, respectively. The latter feature does not vanish completely in the nonlinear spectrum of the spiropyran form, possibly because of the existence of some photoconversion caused by the laser beam during the measurements. A nonlinear absorption peak at 900 nm is found in the spiropyran form with an effective cross section of about 20 GM; it is likely due to three-photon absorption or to absorption by some intermediate species. The experimental data are supported by calculations performed with the use of a hybrid quantum mechanics-molecular mechanics approach.
authors.affiliation: Institute of Physical and Theoretical Chemistry, Wrocław University of Technology , Wyb. Wyspiańskiego 27, PL-50-370 Wrocław, Poland.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Matczyszyn
authors.forename: Joanna
authors.initials: J
authors.lastname: Olesiak-Banska
authors.forename: Keitaro
authors.initials: K
authors.lastname: Nakatani
authors.forename: Pei
authors.initials: P
authors.lastname: Yu
authors.forename: N Arul
authors.initials: NA
authors.lastname: Murugan
authors.forename: Robert
authors.initials: R
authors.lastname: Zaleśny
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Roztoczyńska
authors.forename: Joanna
authors.initials: J
authors.lastname: Bednarska
authors.forename: Wojciech
authors.initials: W
authors.lastname: Bartkowiak
authors.forename: Jacob
authors.initials: J
authors.lastname: Kongsted
authors.forename: Hans
authors.initials: H
authors.lastname: Ågren
authors.forename: Marek
authors.initials: M
authors.lastname: Samoć