From chemistry-request@server.ccl.net Thu Oct 4 05:58:45 2001 Received: from mel.ruc.dk ([130.225.220.27]) by server.ccl.net (8.11.6/8.11.0) with ESMTP id f949wiB19717 for ; Thu, 4 Oct 2001 05:58:44 -0400 Received: from smtprelay.ruc.dk (smtprelay.ruc.dk [130.225.220.22]) by mel.ruc.dk (8.9.3/8.9.1) with ESMTP id LAA19484; Thu, 4 Oct 2001 11:58:43 +0200 (MET DST) Received: from virgil.ruc.dk (virgil.ruc.dk [130.225.220.110]) by smtprelay.ruc.dk (8.9.3+Sun/8.9.3) with ESMTP id LAA06806; Thu, 4 Oct 2001 11:34:43 +0200 (MEST) Received: from VIRGIL/SpoolDir by virgil.ruc.dk (Mercury 1.47); 4 Oct 01 11:58:43 +0100 Received: from SpoolDir by VIRGIL (Mercury 1.47); 4 Oct 01 11:58:38 +0100 From: "Jens Spanget-Larsen" Organization: Roskilde Universitetscenter To: Ali Rashid Date: Thu, 4 Oct 2001 11:58:24 +0100 Subject: CCL:Linear dichroism. CC: chemistry@ccl.net X-Confirm-Reading-To: "Jens Spanget-Larsen" X-pmrqc: 1 Priority: normal X-mailer: Pegasus Mail for Windows (v2.23) Message-ID: Ali Rashid: > Hi, I was wandering if anyone knows of a way to simulate the > absorption spectra of a system. What i am interested in is, starting > from a model of a molecules or molecules packed in a certain way, > can i then calculate things like the dichroic ratio and the linear > dichroism? Thank you in advance. -- Dear Ali, In principle, transition energies, oscillator strengths and transition moment directions of molecular optical transitions can be predicted by quantum chemical calculations (the presence of molecular symmetry elements may be of great help in this task). It is then possible to predict the dichroic ratio and the linear dichroism of an assembly of molecules "packed in a certain way", since the resulting absorption probability is proportional to the cosine-squared of the angle between the individual moment directions and the electric vector of the linearly polarized light. See the volume by Michl and Thulstrup: J. Michl, E. W. Thulstrup: "Spectroscopy with Polarized Light. Solute Alignment by Photoselection, in Liquid Crystals, Polymers, and Membranes", VCH Publishers 1986, 1995 (ISBN 1-56081-910-3). Yours, Jens >--< =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- JENS SPANGET-LARSEN Office: +45 4674 2710 Department of Chemistry Fax: +45 4674 3011 Roskilde University (RUC) Cell-Phone: +45 2320 6246 P.O.Box 260 E-Mail: JSL@virgil.ruc.dk DK-4000 Roskilde, Denmark http://virgil.ruc.dk/~jsl =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-