1. Quantum Rotational Dynamics of CH 3 I Group D Y Liu, S Jonas, V Atakan, H Wu, S Omar-Diallo, I-K. Jeong D. Phelan

2. System description Methyl IodideThree fold potential model V3

3. Numerical Values of Energy Level

4. Experimental Goals What we are looking for: 1. The “height”of the V3 well 2. The librational energy 3. The projected radius of Hydrogen from Carbon

5. Why HFBS and FANS? The tunneling energy is quite small Tunneling process have energies on order of ~  eV The HFBS has high resolution. ~1  eV, well below the conventional triple-axis and neutron TOF spectrometers. The FANS has high energy transfer (~100meV)

6. HFBS and FANS diagram:

7. How HFBS works The HFBS varies incident energy by using a cam-based Doppler-driven monochromator. Phase Space Transformer increase flux 4x. Very large analyzer array, 20% of 4  The scattering chamber is operated under vacuum instead of Ar or He improving the signal-to- background ratio.

8. Tunneling Energy: ~2.3  eV V3 ~ 42meV Inelastic Scattering (T = 8K)

9. R exp =1.03A R cal =1.027A Elastic and Quasielastic PeakEISF Fitting Quasielastic Analysis (T = 38K) Jump Diffusion Model:

10. Librational Energy Study by FANS 1 st libration energy: ~14meV

11. Acknowledgement NIST Zema Chowdhuri, Robert Dimeo (HFBS) Craig Brown (FANS) Members of Group D, summer school 2003