Research efforts on a variety of projects concentrate on the use of fluorescence spectroscopy of jet-cooled molecules and Fourier transform infrared (FT-IR) and laser Raman spectroscopies. Computer methods for quantum mechanical calculations and on-line instrument control are also utilized and developed.
The dynamics of conformational energy changes in electronic ground and excited states are investigated by analyzing the far-infrared, mid-infrared, Raman and fluorescence data using quantum mechanical computational techniques. Such investigations on molecules, which possess large-amplitude motions such as ring inversions or internal rotations, lead to the determination of the equilibrium structures, potential energy barriers, pathways of interconversion and intramolecular forces. Recent work has focused on molecules that require two vibrational coordinates to define their conformations. For example, the conformational changes of cyclopentanes and cyclohexenes containing heteroatoms can be investigated using far-infrared and Raman spectra along with two-dimensional potential energy calculations.
A tunable Nd:YAG based OPO laser system is used to study the conformations of molecules in electronic excited states. A supersonic jet system cools the molecules so that vibrational excited states are thermally depopulated. Fluorescence excitation spectra and ultraviolet absorption spectra, such as those shown below for 1,3-benzodioxole, can be recorded and analyzed to determine the vibrational potential energy surfaces for the electronic excited states of interest. The ultraviolet absorption spectra also shown below nicely complement the fluorescence studies. Dispersed fluorescence spectra aid in the analyses of the ground states. This type of information helps to better understand molecular properties and photochemical pathways in electronic excited states.
J. Laane, Editor, Frontiers of Molecular Spectroscopy, Elsevier Publishing, Amsterdam, The Netherlands, 706 pp. (2009). Includes chapter "Vibrational Potential Energy Surfaces in Electronic Excited States" by J. Laane, pp.63-132.
"Intramolecular π-type hydrogen bonding and conformations of 3-cyclopenten-1-ol. 1. Theoretical calculations." A.A. Al-Saadi, E.J. Ocola, and J. Laane, J. Phys. Chem. A, 114, 7453-7456 (2010).
"Intramolecular π-type hydrogen bonding and conformations of 3-cyclopenten-1-ol. 2. Infrared and Raman spectral studies at high temperatures." E.J. Ocola, A.A. Al-Saadi, C. Mlynek, H. Hopf, and J. Laane, J. Phys. Chem. A, 114, 7457-7461 (2010).
"Spectroscopic Investigations and Potential Energy Surfaces of the Ground and Excited Electronic States of 1,3-Benzodioxan." K. McCann, M. Wagner, A. Guerra, P. Coronado, J.R. Villareal, J. Choo, S. Kim, and J. Laane, J. Chem. Phys., 131, 044302/1-9 (2009).
"Spectroscopic Investigation of the Molecular Vibrations of 1,4-Dihydronaphthalene in its Ground and Excited Electronic States." M.Z.M. Rishard, M. Wagner, J. Choo, and J. Laane, J. Phys. Chem. A, 113, 7753-7759 (2009).
"Ultraviolet Absorption Spectra of Pyridine-d0 and –d5 and Their Ring-Bending Potential Energy Function in the S1(n,π*) State." P. Boopalachandran and J. Laane, Chem. Phys. Lett., 462, 178-182 (2008).
"Ultraviolet Cavity Ringdown Spectra and the S1(n,π*) Ring-Inversion Potential Energy Function for 2-Cyclohexen-1-one-d0 and its 2,6,6-d3 Isotopomer." M.Z.M. Rishard, E.A. Brown, L.A. Ausman, S. Drucker, J. Choo, and J. Laane, J. Phys. Chem. A, 112, 38-44 (2008).
"Spectroscopic Determination of Vibrational Potential Energy Surfaces in Ground and Excited Electronic States." J. Yang and J. Laane, J. Elec. Spectrosc. and Related Phenomena, 156-158, 45-50 (2007).
"Spectroscopic and Computational Studies of the Intramolecular Hydrogen Bonding of 2-Indanol." A.A. Al-Saadi, M. Wagner, and J. Laane, J. Phys. Chem. A, 110, 12292-12297 (2006).