Jaan Laane
Professor
Ph. D., Massachusetts Institute of Technology
Contact
Information:
Department of Chemistry
Texas A&M University
College Station, TX 77842
Phone:
(979) 845-3352
Fax: (979) 845-3154
laane@chem.tamu.edu
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.
"Vibrational Spectra, DFT Calculations, Unusual Structure, Anomolous CH2 Wagging and Twisting Modes, and Phase-Dependent Conformation of 1,3-Disilacyclobutane." M.Z.M. Rishard, R.M. Irwin, and J. Laane, J. Phys. Chem. A, 2007, 111, 825-831.
"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, 2006, 110, 12292-12297.
"Laser Induced Fluorescence Spectra, Structure, and the Ring-Twisting and Ring-Bending Vibrations of 1,4-Benzodioxan in its S0 and S1(π,π*) States." J. Yang, M. Wagner, and J. Laane, J. Phys. Chem. A, 2006, 110, 9805-9815.
"Fluorescence and Ultraviolet Absorption Spectra and Structure of Coumaran and its Ring-Puckering Potential Energy Function in the S1(π,π*) State." J. Yang, M. Wagner, K. Okuyama, K. Morris, Z. Arp, J. Choo, N. Meinander, and J. Laane, J. Chem. Phys., 2006, 125, 034308.
"Lowest η,π* Triplet State of 2-Cyclopenten-1-one: Cavity Ringdown Absorption Spectrum and Ring-Bending Potential Energy Function." N. Pillsbury, J. Choo, J. Laane, and S. Drucker, J. Phys. Chem. A, 2003, 107, 10648-10654.
"Laser-Induced Fluorescence, Electronic Absorption, Infrared and Raman Spectra, and Ab Initio Calculations of 1,2-Dihydronaphthalene. Investigation of the Out-of-Plane Ring Modes for the Ground and S1 (π, π*) Excited States." D. Autrey, Z. Arp, J. Choo, and J. Laane, J. Chem. Phys., 2003, 119 (5), 2557-2568.
"Feature Article: Experimental Determination of Vibrational Potential Energy Surfaces and Molecular Structures in Electronic Excited States." J. Laane, J. Phys. Chem., 2000, 104A, 7715-7733.
"Spectroscopic Determination of the Vibrational Potential Energy Surface and Conformation of 1,3-Benzodioxole in its S1(π,π*) Excited State. The Effect of the Electronic Excitation on the Anomeric Effect." J. Laane, E. Bondoc, S. Sakurai, K. Morris, N. Meinander, and J. Choo, J. Amer. Chem. Soc., 2000, 122, 2628-2634.
