Vibrational Potential Energy Surfaces and Molecular Structures In Electronic Excited States

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The Experimental Physical Chemistry Program supports Prof. Jaan Laane of Texas A&M University in his continuing studies of molecules with large-amplitude vibrations. He will use fluorescence excitation spectroscopy, sensitized phosphorescence excitation spectroscopy and two-photon spectroscopy with photon or ionization detection to map the energy levels of the excited states. He will focus on cyclic and multicyclic carbonyl compounds and aromatic molecules, especially those molecules with two chromophores and closely lying electronic states or those molecules exhibiting interesting structural changes such as photoracemization or photoisomerization. Laane will also use dispersed fluorescence and far-IR and Raman spectroscopies to obtain complementary information on the ground state surfaces, and molecular mechanics (MM3) and ab initio calculations to predict potential energy surfaces and structures. An improved understanding of electronic excited states is important for providing a better perspective of photochemical and other important chemical processes as well as on chemical bonding and structure in general. Determination of the potential energy surfaces for the excited states will provide detailed insight into the energetics and interactions associated with these states. The experimental work to be carried out here will provide the data necessary for calculating the potential energy surfaces and will also further help improve our experimental procedures for collecting this type of spectroscopic information. Results on molecules in triplet states or on molecules that undergo interesting structural changes upon absorption should provide fundamental information that has not been readily attained in the past.