SIMULATION OF THE SPIN-VIBRONIC STRUCTURE IN THE GROUND ELECTRONIC STATE AND EMISSION SPECTRA INTENSITIES FOR CH 3 O RADICAL VADIM L. STAKHURSKY Radiation Oncology, Duke University Clinic, DUMC 3295, Durham, NC XIAOYONG LIU, VLADIMIR A. LOZOVSKY †, ILIAS SIOUTIS, C. BRADLEY MOORE *, and TERRY A. MILLER Laser Spectroscopy Facility, Department of Chemistry, The Ohio State University 120 W. 18th Avenue, Columbus OH † Deceased * Northwestern University, Evanston, IL,

Motivation 1. Jahn-Teller distortion can significantly affect the characteristics of the molecule, e. g. rotational and vibrational spectra, partition function, rate of chem. reaction, enthalpy 2. Because of the relatively small size we use methoxy as a benchmark system for analysis of various effects of coupling of electronic and vibrational motion, e. g. Jahn- Teller effect, Herzberg-Teller effect, etc.. 3. We develop a generic throughput application for fast data analysis of a wide variety of JT active systems.

Harmonic potentialJT distorted potential

Vibrational frequencies of CH 3 O 2948 a cm cm b cm cm cm cm cm cm cm cm cm cm -1 symmetric C-H stretchCH 3 umbrella C-O stretch asymmetric C-H stretchscissorsCH 3 rock a D. E. Powers, M. B. Pushkarsky and T. A. Miller, J. Chem. Phys. 106, 6863 (1997). b S. C. Foster, P. Misra, T.-Y. Lin, C. P. Damo, C. C. Carter, and T. A. Miller, J. Phys. Chem. 92, 5914 (1988).

Pseudo Jahn-Teller where coupling matrix elements can be calculated as and ladder operator PJT Hamiltonian C.F. Jackels, J. Chem. Phys. 76, 505 (1982). E+E+ E-E- A E Optical transition Same effect can be described via Herzberg- Teller effect, that is when transitional dipole moment has dependency along vibrational coordinate:

Spin-vibronic Hamiltonian e e+e+ e-e- Less frequently used terms: where Standard:

SOCJT as a tool for JT problem analysis What is SOCJT? Fortran code for multidimensional Jahn-Teller problem with/without spin-orbit interaction SOCJT gives:  Positions of spin-vibronic levels of the molecule in degenerate electronic state  Insight into composition of the level in terms of harmonic oscillator quantum numbers |v, l> providing a tool for levels “labeling”  Calculates UV spectrum for absorption or emission experiments SOCJT input: PES parameters up two third order: Harmonic frequencies ω i and anharmonicities Linear JT parameters, D i Quadratic JT parameters, K i, and cross-quadratic terms for interaction of degenerate vibrations Bilinear terms for coupling of symmetric and degenerate modes Fermi iteraction terms Q 3 Terms Q 3 non-diagonal in the projection of the electronic orbital momentum Spin-Orbit coupling parameter a  e.

Establishing the PJT parameters, DF pumped via 3 5 PJT explains appearance of A 1 and A 2 levels of vibrations v 6, v 5 and v 4.

Simulations of DF spectrum pumped via PJT explains appearance of origin and CO stretch progression in the spectrum

Establishing the PJT parameters, DF pumped via No significant difference

Establishing the PJT parameters, DF pumped via No significant difference

ConstantThis workRef. a Ref. b Ref. d A so c -134 ω6ω D6D K6K ω5ω D5D K5K ω4ω D4D < K4K ω1ω b a T. A. Barckholtz and T. A. Miller, J. Phys. Chem. A 103, 2321 (1999). b U. Höper, P. Botschwina and H. Köppel, J. Chem. Phys. 112, 4132 (2000) and J. Schmidt-Klügmann, H. Köppel, S. Schmatz and P. Botschwina, Chem. Phys. Lett. 369, 21 (2003). c This value was introduced phenomenologically to match the separation of the vibrationless spin-doublet in work b. d A. V. Marenich and J. E. Boggs, J. Chem. Phys. 122(2), (2005). Determined constants and comparison with ab-initio ConstantThis work   0.24  0.27 A so, ω i (i=1, 4-6) and b 14 in cm -1

Conclusions and future work 1.We extended the SOCJT VIEW code to compute intensities of the vibronic transitions with correction for pseudo Jahn-Teller effect. The coefficients for coupling along different degenerate vibrational coordinates are extracted from the experimental spectra. 2. The PJT corrections to intensities are important in analysis of DF spectrum excited through symmetric level 3 5, and through CH stretch fundamental , but insignificant for simulations of spectra excited through and The PJT correction approach has to be applied to the analysis of the vibronic Spectra of CHD 2 O (NEXT TALK). THANK YOU

ACKNOWLEDGMENTS Ohio State University

SOCJT GUI hybrid capabilities SOCJT code is interfaced to spectra simulation and visualization package SpecView The features of the product:  Simulate vibronic structure in degenerate electronic state of a C nv molecule with up to 7 Jahn-Teller active vibrational modes and up to 5 non-active modes  Simulate intensities of vibrational features observed in dispersed fluorescence (DF) and absorption spectra  Fast calculation of spectra (2-5 sec for region up to 3000 cm -1 in methoxy)  Ability to run non-linear least square fit of simulated lines to frequencies of observed features (Levenberg-Marquardt method).