1. Production and Storage of Polarized H2, D2 and HD Molecules
by Ralf Engels
JCHP / Institut für Kernphysik, FZ Jülich
Dr. Ralf Engels

2. with momenta up to 3.7 GeV/c
p, p, d, d
with momenta up to 3.7 GeV/c
internal experiments –
with the circulating beam
external experiments –
with the extracted beam

3. PIT @ ANKE/COSY Main parts of a PIT: Atomic Beam Source
Target gas
hydrogen or deuterium
H beam intensity (2 hyperfine states)
atoms / s
Beam size at the interaction point
σ = 2.85 ± 0.42 mm
Polarization for hydrogen atoms
PZ = ± (HFS 1)
PZ = ± (HFS 3)
Lamb-Shift Polarimeter
Storage Cell
M. Mikirtychyants et al.; NIM A 721 (0) 83 (2013)
Dr. Ralf Engels

4. Pm = ½ Pa Polarized H2 Molecules Pm β= Pa
Measurements from NIKHEF, IUCF, HERMES show that recombined molecules retain fraction of initial nuclear polarization of atoms! Pm Pa β=
Pm = ½ Pa
The HERMES Collaboration; Eur. Phys. J. D 29, 21–26 (2004)
DOI: /epjd/e

5. Pm = 0.5 Pa Polarized H2 Molecules Eley-Rideal Mechanism
Is there a way to increase Pm P
(surface material, T, B etc)?

6. Pol. Molecules: The experimental setup
ISTC Project # 1861 PNPI, FZJ, Uni. Cologne
DFG Project: 436 RUS 113/977/0-1
H2+, D2+
HD+, H3+
p, d

7. The experimental Setup
The Lamb-shift Polarimeter
mI = +1/2
N+1/2 – N-1/2
N+1/2 + N-1/2 P=
mI = -1/2
R. Engels et al., Rev. Sci. Instr. 74 4607 (2003)
R. Engels et al., Rev. Sci. Instr  (2014)

8. The experimental setup
The Lamb-shift Polarimeter H2
H H2+ H2S H2S (α1)
H+ H+ H2S H2S (α1)
Efficiency
∙ ∙ = 5 ∙ 10-12
∙ = 2 ∙ 10-11
See talk by L. Huxold at 10th of September (6 pm, Room A9)

9. ( ) Pm(B,n) = Pm0 P(B,n) = Pm · e
Polarized H2 Molecules
Polarization losses of the molecules due to:
spin-spin (I↔I) interactions of the nucleons
Interaction of the nuclear spins I with the
rotational magnetic moment J
Interaction with the external magnetic field B …
Nuclear Polarization of Hydrogen Molecules from
Recombination of Polarized Atoms
T.Wise et al., Phys. Rev. Lett. 87, (2001).
n ≈ 1000
Naive Model:
P(B,n) = Pm · e
- n
( ) 2 Bc B 1
1+(Bc/B)2 ∙ n/ln 2
Pm(B,n) = Pm0
with: Bc = 5.4 mT, n ≡ average amount of wall colissions

10. Theory

11. p Experimental results
Measurements on Fomblin Oil (Perfluoropolyether PFPE)
HFS 3
TCell = 100 K
Pm = -0.87
Pm = ± 0.02
n = 174 ± 19
c = ± 0.005 p H 2 +
Pm = ± 0.02
n = 277 ± 31
R. Engels et al., Phys. Rev. Lett  (2015)
Dr. Ralf Engels

12. Recombination on Fomblin (?). . . .
Bext . F F F F
C - O - C - O - C O --C
Fused Quarz
Dr. Ralf Engels

13. HD Molecules Pz (D) = -0.3 Pzz (D) = 0.12 Pz (H) = -0.21 D H H
(Surface: Gold / T = 80 K / B = T / E = 2 keV)
Pz (D) = -0.3
Pzz (D) = 0.12
Pz (H) = -0.21 H D H

14. HD Molecules
(Surface: Gold / T = 80 K / B = T / E = 2 keV) H D H

15. HD Molecules Signal of the Photomultiplier [a.u.]
Surface: Fomblin on Fused Quarz
T = 80 K / B = T / E = 0.3 keV
Pz (H) =
Pz (D) =
Pzz (D) =
Signal of the Photomultiplier [a.u.]

16. HD Molecules

17. H H D D Brot Brot H D Brot Bc ~ Brot / r3 Bc (H2) Bc (HD) = 2.4 = 3.4
HD Molecules H H D D
Brot
Brot
Naive Approximation:
Distance Brot <-> H increased by 1/3
Distance Brot <-> D decreased by 1/3
Bc ~ Brot / r3
2/3
1/3 H D
Brot
Bc (H2)
Bc (HD)
= 2.4
= 3.4

18. Experimental Results for Mass 3
Pz =
Preliminary

19. Production of polarized D2 and HD ice possible?
T= 3-10K
Cold
Head
D2 ice
Polarization Measurement:
NMR – Sensor
Dr. Ralf Engels

20. Conclusion We can measure:
the polarization of atoms and molecules in a storage cell.
the recombination of hydrogen/deuterium atoms on
different surfaces and for different HFS.
If Bc is known: the number of wall collisions of the
molecules in the cell.
Pay attention: Other depolarizing effects, e.g. magnetic
impurities on the surface or charged islands on isolating
surfaces, will increase the Bc.

21. Conclusion We can produce polarized H2, D2 and HD molecules with
large vector- and tensor-polarization (~ 0.8) in many
spin combinations.
For what it is usefull?
1.) More dense polarized targets.
2.) Spectroscopy of the molecules or molecular ions
(Contact with the University of Düsseldorf).
3.) New insights in chemical reactions / surface physics.
4.) Polarized fuel to increase the energy output of
Fusion reactors. -> see talk on Wednesday, 2:30 pm
5.) Polarized targets for laser acceleration.
-> see talk by M. Büscher on Wednesday, 5:05 pm
6.) EDM measurements ?
7.) An option to produce polarized molecules for medical application ?