This document discusses an experiment using the Disc Chopper Spectrometer to probe the motion of hydrogen atoms in Mn[N(CN)2]2.pyrazine. The goals were to obtain the crystal structure as a function of temperature using deuterated samples, and to observe single particle motion and vibrations using protonated samples. Data was collected at various temperatures and fitted using DAVE to determine parameters like the elastic incoherent scattering function and effective rotation radius of hydrogen atoms. The analysis found a good value for the rotation radius using a two-fold model.

1. Experiment using the Disc
Chopper Spectrometer
Rotational Ligand Dynamics
Group D
S. Diallo, I-K. Jeong, S. Jonas, D. Phelan, Y. Liu, V. Atakan, H. Wu

2. Our system: Mn[N(CN)2]2.pyrazine
. At 408 K
- Large Debye-Waller Factor on
pyrazine
-Phase transition
•At 435 K Decomposes and loses
pyrazine

3. Experiment
• The goal is to probe the motion of the
Hydrogen atoms in Mn[N(CN)2]2.pyrazine.

4. DCS: TOF instrument
Neutron Guide
Optical Filter
Sample Chamber
913 3He detectors,
400x31x11mm3
Monochromatic
Beam Monitor
Radial Collimator
Sample
Monochromating Choppers
Frame Overlap
Chopper
Order Removal
Choppers
Pulsing Choppers
Argon gas-filled
Flight Chamber
White Beam
Monitor
Crystal Filter
Transmitted
Beam Monitor
Beam
Stop
Shutter

5. Measurement and Data Analysis
• Deuterated sample for coherent Bragg diffraction
to obtain structure as a function of temperature
and paramagnetic structure
• Protonated to observe both single particle motion
(quasielastic) and to weigh the inelastic scattering
spectrum in favor of hydrogen (vibrations)

6. Protonated Data fitting using
DAVE
Ao = ½[1+sin(2Qr)/(2Qr)]
EISF!!
0 1 2 2
1 2
( , ) ( )
4
S Q A A

  
  
 

QISF!!
At T= 425 K

7. Elastic Incoherent Scattering
Function (EISF)
T=425K, Fitting of EISF, Eq: p0 + p1 * sin(p2*x)/(p2*x)
R=p2=3.86(3)A

8. Conclusions and further
considerations
• In our fitting, we did find a good value of
the rotation radius using the two-
fold model.

9. Thanks to all the NCNR staff for
their help and support.