## Wednesday, May 28, 2008

### Two-photon absorption strength

THE JOURNAL OF CHEMICAL PHYSICS 124, 204104 , 2006.

jchemphys_124_2041041

Two-photon absorption strength: A new tool for the quantiﬁcation of two-photon absorption

Rémy Fortrie

Laboratoire de Chimie, UMR 5182 du CNRS, École Normale Supérieure de Lyon, 46 Allée d’Italie, F-69364 Lyon Cedex 07, France

Henry Chermettea

Université Claude Bernard Lyon 1 and UMR 5182 du CNRS Chimie Physique Théorique, Bât. Paul Dirac (210), 43 Boulevard du 11 Novembre 1918, F-69622 Villeurbanne Cedex, France

Received 21 December 2005; accepted 29 March 2006; published online 22 May 2006��

In this paper, we deﬁne the two-photon absorption strength, a new characterization tool, similar to the oscillator strength, but for two-photon absorption. It allows the quantiﬁcation of the two-photon absorption properties of molecular systems which are one-photon transparent. Its deﬁnition is such that the corresponding numerical values are around 100 for small molecules. We also show that this new theoretical tool allows the direct comparison of experimental and theoretical data without requiring the introduction of any arbitrary band width. As an example, the experimental and theoretical ��AM1 + CNDO / S and HF + CIS / 3-21G�� two-photon absorption properties of the 2 , 2��-bi��9,9-dihexylﬂuorene�� molecule are compared. © 2006 American Institute of Physics. ��DOI: 10.1063/1.2198530�� THE JOURNAL OF CHEMICAL PHYSICS 124, 204104 ��2006��