From owner-chemistry[ AT ]ccl.net Fri Dec 21 14:18:00 2007 From: "Ramon Crehuet rcsqtc^iiqab.csic.es" To: CCL Subject: CCL:G: Time dependent properties Message-Id: <-35907-071221113324-22448-OSczvPHDGoWQxzbJIcczFg^-^server.ccl.net> X-Original-From: Ramon Crehuet Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1; format=flowed Date: Fri, 21 Dec 2007 16:36:35 +0100 MIME-Version: 1.0 Sent to CCL by: Ramon Crehuet [rcsqtc(_)iiqab.csic.es] Dear CCLers, I was helping a colegue in the interpretation of an absorption spectra. I used TD-DFT for the singlet states. Now she asked me to consider a low-lying triplet. I checked and saw that Gaussian can do triplets and singlets with the option 50-50. If I am not wrong, this singlet-triplet transitions are only allowed by the spin-orbit coupling, therefore a 'normal' calculation will always give a null oscillator strength. Am I right about that? What would then be the easyiest way to proceed from here? Thanks in advance, Ramon