1. Characterisation and Control of Cold Chiral Compounds
Chris Medcraft
“Structure and Dynamics of Cold and Controlled Molecules”
Center for Free-Electron Laser Science, Hamburg
Max-Planck-Institut für Struktur und Dynamik der Materie, Hamburg

2. General Technique Fourier Transform Microwave Spectroscopy

3. Fourier Transform Microwave Spectroscopy
Chirped Pulse FTMW
Cavity Based FTMW
Chirped Excitation signal
2-8.5 GHz from AWG
300W TWT Amplifier
Molecular response measured directly by fast oscilloscope
Full spectrum in one shot
≈ 40 kHz resolution
Cavity resonance amplifies excitation and molecule signals
6-40 GHz range
Molecular response mixed down to radio frequency
1 MHz of spectrum measured at once
≈1 kHz resolution
Brown et. Al., Rev. Sci. Instrum. 79, (2008)
Grabow et al., Rev. Sci. Instrum. 76,  (2005)

4. Chiral Molecules to study Parity Violation
Arises from the weak interaction
Test of fundamental physics
Small difference in energy between enantiomers
Measureable difference in rotational transitions
Large atoms increase the effect dramatically
Δ pv ∝ Z eff
M. Quack, Angew. Chem. 114 (2002) 4812

5. Universität Regensburg
Target molecules
CpRe(CO)(NO)I
Two heavy atoms
Predicted Enantiomeric Energy difference: 316 Hz[1]
Enantiomer separation may be difficult Re I N O C
Prof. Dr. Robert Wolf
Universität Regensburg
[1]P. Schwerdtfeger, J. Gierlich, T. Bollwein, Angew. Chem. Int. Ed. 42 (2003) 1293.
P. Schwerdtfeger, R. Bast, J. Am. Chem. Soc. 126 (2004) 1652.

6. Target molecules 187Re (62.6%) Spin = +5/2 185Re (37.4%)
127I, Spin = +5/2
14N, Spin = +1
Ab initio
Rotational Constants
A=759.9 MHz
B=423.2 MHz
C=379.4 MHz
Rotational
Temp=0.5 K
187Re Simulation
185Re Simulation

7. CpRe(CO)(NO)(CH3) Results
187Re (62.6%), Spin = +5/2
185Re (37.4%), Spin = +5/2
14N, Spin = +1
Chirped Pulse Broadband FTMW

8. Nuclear Quadrupoles J+IRe=F1 F1+IN=F Ratio of 185Re / 187Re
Quantum Numbers: J, Ka, Kc, F1, F F1
F = Total angular momentum
Ratio of 185Re / 187Re
Mass = 98.9%
A,B,C = %
Q = 105.5% J

9. Rhenium Nuclear Quadrupole Hyperfine Splitting

10. Nitrogen Nuclear Quadrupole Hyperfine Splitting

11. Results

12. Cavity 600 mm mirrors 1 m separation 6-40 GHz 1 MHz modes
Resolution ≈1 kHz
Require <10 Hz
1 metre

13. Transit time broadening ≈ 150 Hz
Resolution
Doppler width
≈1 kHz at 10 GHz
δv=30-50 m/s
δv=15-20 m/s
Transit time broadening ≈ 150 Hz

14. Helium Buffer Gas Or: Microwave focussing and deceleration
Chamber at ≈ 4 K
John Doyle and Dave Patterson - Harvard University (Unpublished)
Or: Microwave focussing and deceleration
Merz et. al., Phys. Rev. A 85,  

15. Summary Experimental design Aims Preliminary Results
Characterisation of heavy molecules
Parity violation
Preliminary Results
CpRe(NO)(CO)(CH3)

16. Acknowledgements FD02 WA 03 Chris Medcraft Thomas Betz Alvin Shubert
Melanie Schnell
FD05
Simon
Merz
Jack Graneek
Sabrina
Zinn
David Schmitz

17. Acknowledgements Robert Wolf - Universität Regensburg
Jens-Uwe Grabow - Leibniz Universität Hannover

18. Slow molecules
δv=1-3 m/s
vDoppler= Hz
vtransit ≈ 3 Hz

19. Electronics

20. No Off-diagonal Re NQCC χab and χbc
χab , χbc

21. Calculations Rhenium (Z=75) Nuclear quadrupole coupling
Lots of electrons!
Requires relativistic correction
Nuclear quadrupole coupling
Can’t use pseudopotentials
Large off diagonal terms for Rhenium
Internal rotations
Methyl
Cyclopentadienyl
Basis Set
*no relativistic
correction