Download - High-resolution imaging of C-He and C-H2
High-resolution imaging of C-He and C-H2collisions using a Zeeman decelerator
V. Plomp1, X.-D. Wang1, F. Lique2, J. Kłos3, J. Onvlee1 and S. Y. T. van de Meerakker11Institute for Molecules and Materials, Radboud University Nijmegen, The Netherlands;
2Institut de Physique de Rennes, Université de Rennes, France; 3Department of Chemistry and Biochemistry, University of Maryland, U.S.A.
E-mail: [email protected], [email protected]
Technical support: N. Janssen, E. Sweers, A. van Roij, G. WulterkensAcknowledgements & References
Testing models of molecular interactions with high-resolution crossed beam scattering experiments.
Extend the diversity of these scattering experiments to paramagnetic species, with the use of a Zeeman decelerator.
1. Goals
6. C-H2 collisions (3P1 3P0) - Preliminary
[1] Mol. Phys. 119, e1814437 (2020)[2] Phys. Rev. A 98, 033406 (2018)[3] Instrum. Sci. Technol. 28, 85 (2000)[4] Nat. Chem. 6, 216 (2014)
7. Conclusion & OutlookWe developed an e�cient recoil-free detection scheme for C 3PJ
atoms. Combined with Zeeman deceleration & VMI this allows for high-resolution imaging of C-He and C-H2 collisions, where we directly observe di�raction oscillations and rapid changes in the angular scattering distribution with changing energy. Excellent agreement is found with simulations based on ab initio calcula-tions of the cross sections.We aim to extend this experiment to investigate scattering reso-nances in low-energy C-He and C-H2 collisions and image reactive collisions of C with O2.
4. Recoil-free C-atom REMPI
2p2 3PJ
2p3p 3PJ 2p3s 3PJ
I.P. (2P0J)
~280
nm
~165
nm(V
UV
)
~212
nm
~296
nm
~329
nm
Four-wave mixing [3] of 212 nm and 296 nm in a Kr gas cell gener-ates 165 nm VUV. Subsequent threshold ionization by ~329 nm ena-bles e�cient high-resolution detection.
Rydbergresonances
2P01/2 step
2P03/2 step
Ionizing laser wavelength (nm)
Imaged decelerated C3P1 beam v║=300 m/s2+1 (280 nm) VUV + 212/296 VUV + 329
v║ (50 m/s)
v ┴ (5
0 m
/s)
0%
100%
3. Zeeman deceleratorThe Zeeman shift in paramagnetic species allows the use of strong, pulsed magnetic �elds (>2.5 T) to state-selectively decelerate [2] providing high-state-purity beams with narrow velocity spreads.
Alternating array of:
Pulsed solenoidsa
- Used to guide/decelerate - Longitudinal (║) focussing
Permanent hexapolesb
- Transverse (┴) focussing independent of solenoidsZe
eman
shi
ft
Longitudinal position
a ab
Computer controlledC-atom 3P1 state
longitudinal velocity (v║)Simulation
Experiment
Guiding
Hybrid
Deceleration
v║=700 m/s
600 500450
v║=400 m/s
350300
250
Coils off
2. Crossed beam setup
VMI [1]: maps the velocityof scattered C 3PJ revealing itsangular & radial distribution
5. C-He collisions (3P1 3P0)
Di�raction oscillations [4]
45°
COM
He velocity C 3P1velocity
Relative velocity
3P1 3P03P2 3P0
0%
100%Ecol=31.7 cm-1 52.4 cm-1 86.4 cm-1
(deg.)
V∥(m/s)
FWHM V∥
(m/s)FWHM V⟂
(m/s)
Exp. Sim. Exp. Sim.
700 15.6 13.8 10.0 7.3
600 13.5 13.1 9.7 7.4
500 12.2 11.9 11.5 10.4
450 9.2 8.8 10.9 11.7
400 11.7 11.8 7.7 8.6
350 6.7 6.6 8.9 7.3
300 4.8 3.9 7.8 9.9
250 4.1 2.1 8.0 7.2
Simulations based on ab initiocalculations of the cross sections
0%
100%
Ecol=32.3 cm-1 33.1 cm-1 36.3 cm-1
40.2 cm-1 51.7 cm-1
J=2, +43.4 cm-1
J=1, +16.4 cm-1
J=0, 0 cm-1
(400 m/s)
(400 m/s)
