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QUANTUM ROTATIONS IN METHYL IODIDE: A Study Using HFBS and FANS

QUANTUM ROTATIONS IN METHYL IODIDE: A Study Using HFBS and FANS. Group C Christopher Kitchens Yifu Ding Amit Kumar Joon Ho Roh. High Flux Backscattering Spectrometer. High Flux Backscattering Spectrometer. resolution ~ 1 μeV energy transfers upto ±50 μeV motions on ns timescales

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QUANTUM ROTATIONS IN METHYL IODIDE: A Study Using HFBS and FANS

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  1. QUANTUM ROTATIONS IN METHYL IODIDE: A Study Using HFBS and FANS Group C Christopher Kitchens Yifu Ding Amit Kumar Joon Ho Roh

  2. High Flux Backscattering Spectrometer

  3. High Flux Backscattering Spectrometer • resolution ~ 1 μeV • energy transfers upto ±50 μeV • motions on ns timescales • momentum transfers from 0.25 Å-1 to 1.75 Å-1

  4. BULK CH3I DYNAMICS Inelastic Quasielastic CH3I melting point = 206 K Use 3-fold symmetric potential

  5. HFBS DATA FOR CH3I at T = 8 K V3 = 42 meV Et = 2.3 μeV E ~ 7.5 meV ? Check with FANS

  6. Filter Analyzer Neutron Spectrometer • measures vibrational motion • energy transfers of order 10 to 100 meV • resolution about 1 meV

  7. FANS DATA at T = 12 K Fit Results : Elib = 13.2 meV

  8. HFBS DATA FOR CH3I at T = 40 K

  9. EISF Fitting for T = 40 K data Rfit = 0.965 Å Rexp = 1.03 Å

  10. SUMMARY • HFBS was used to study the rotational dynamics of CH3I. • Tunneling energy was determined using HFBS from which the barrier height and the transition energy for libration was calculated. • Data from FANS was used to verify the prediction of the libration transition energy. • Radius of the methyl group was estimated by fitting the EISF data.

  11. ACKNOWLEDGEMENTS • To NIST and NSF for the opportunity to experiment and study Neutron Spectroscopy and its applications • To the NCNR Summer School Coordinators and Instructors for their assistance and guidance

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