LEE Soo Ying

Professor

Education: B.Sc. (Hons. 1), University of Malaya; Ph.D., University of Chicago, Post-doc: UCLA, FSNAS

Honours: FSNIC, CChem, FRSC, FASc

Research Area: Nonlinear Optical Spectroscopy;
Molecular Reaction Dynamics

Phone: (65) 6513 8466

E-mail: sooying@ntu.edu.sg

Webpage: http://www.spms.ntu.edu.sg/CV/SooYingLEE/


Research Interest

Wave packet theory of ultrafast spectroscopy
The availability of femtosecond pulses and pump-probe techniques have made it possible to directly prepare and monitor coherent vibrational wave packets in the ground and excited electronic states of polyatomic molecules. The dynamic wave packet can be monitored, for example, with a femtosecond probe pulse in absorption or emission, or more recently using a simultaneous pair of picosecond pump and femtosecond probe pulses in stimulated Raman scattering. On the theoretical front, time dependent wave packet methods provide a physically intuitive understanding of the various spectroscopic processes as well as being simple and effective in calculations. Our interest is in the perturbative and nonperturbative wave packet approaches and using reasonable potential energy surfaces to model and calculate the various nonlinear ultrafast spectroscopic processes in photochemical and photobiological systems

Quantum wave packet dynamics in high-dimensions
We are interested in developing quantum wave packet methods in high dimensional space to accurately simulate elementary polyatomic reaction processes, as well as simultaneously constructing accurate potential energy surfaces for the reaction. For example, the powerful time dependent initial state selected wave packet (ISSWP) method will be used to study the important class of reactions: X+CH4 (X=H, D, Cl), including
(a) Reaction probabilities, reaction cross sections, and thermal rate constants for H+CH4abstraction channel using a seven-dimensional model with CH4 initially in various vibrational states.
(b) Extending the calculation to eight dimensions by adding the symmetric vibrational mode of the non-reactive CH3 moiety.
(c) Study isotope effects in the seven-dimensional model for D+CH4, H+CD4, H/D+CHD3 and H/D+CDH3.
(d) Use the seven-dimensional model to study the reaction Cl(2P3/2)+CH4 and its isotopic counterparts.

(A) Calculated temporal evolution of the FSRS difference spectra of CDCl3 for pump-probe delays from 795 – 945 fs in intervals of 15 fs, but with Rayleigh contribution baselines removed so as to better see just the FSRS difference Stokes spectra.
(B) Temporal evolution of the mean position <QA1(t)> of the coherent wave packet created by the impulsive pump pulse on the ground PES for the C-Cl A1 bend.
(C) Same as (B), but for the C-Cl E bend. There is a strong correlation between the wave packet motion and the phase of the FSRS difference spectra.
Both the C-Cl A1 and E sidebands have inversion symmetry about the central Stokes C-D stretch line, in good comparison with experimental results.



Selected Publications

  1. Song, H W, Y P Lu, and S Y Lee, Fully converged integral cross sections of collision induced dissociation, four –centre, and single exchange reactions, and accuracy of the centrifugal sudden approximation in H2 + D2 reaction. Journal of Chemical Physics, 136 (2012): Art. 114307-1 to 9.

  2. Niu, K, and S Y Lee, Analysis of time resolved femtosecond and femtosecond/picosecond coherent anti-Stokes Raman spectroscopy: Application to toluene and Rhodamine 6G. Journal of Chemical Physics, 136 (2012): Art. 064504-1 to 11.[Selected for the Mar 2012 issue of Virtual Journal of Ultrafast Science. Vol. 11, Issue 3.].

  3. Qiu, X Q, X T Li, K Niu, and S Y Lee, Inverse Raman bands in ultrafast Raman loss spectroscopy. Journal of Chemical Physics, 135 (2011): Art. 164502-1 to 8.

  4. Song, H W, Y P Lu, and S Y Lee, Full-dimensional time-dependent wave packet dynamics of H2 + D2 reaction. Journal of Chemical Physics, 135 (2011): Art. 014305-1 to 10..

  5. Zheng, L M, Lu Y P, S Y Lee, H Fu, and M H Yang, Theoretical studies of the N2O van der Waals dimer: ab initio potential energy surface, intermolecular vibrations and rotational transition frequencies. Journal of Chemical Physics, 134 (2011): Art. 054311-1 to 10.

  6. Zhao, B, Z G Sun, and S Y Lee, Quantum theory of time-resolved femtosecond stimulated Raman spectroscopy: Direct versus cascade processes and application to CDCl3. Journal of Chemical Physics, 134 (2011): Art. 024307-1 to 12.
    [Selected for the Feb 2011 issue of Virtual Journal of Ultrafast Science. Vol. 10, Issue 2.]