8-12 July 2019
Cité des Congrès
Europe/Paris timezone

Spectroscopic study of collisions in the 2$^{3}$P state of $^3$He and $^4$He in low pressure gas discharges

Not scheduled
2h 30m
Auditorium 450 (Cité des Congrès)

Auditorium 450

Cité des Congrès

5, rue de Valmy, Nantes, France Site web : https://lacite-nantes.fr/


Ali Dia (Laboratoire Kastler Brossel and Saint Joseph University)


Spin-polarized $^3$He gas has extensive applications*. Metastability exchange optical pumping (MEOP) can indirectly orient the nuclear spin with high efficiency in low pressure gas. A weak discharge excites a small fraction of the atoms to the 2$^3$S metastable state. OP operates on the 2$^3$S-2$^3$P transition and ME collisions transfer polarization to the ground state (gs). In practice MEOP performance is limited by OP-induced polarization loss, as systematically evidenced at high pump light power. Collision-induced population transfer between 2$^3$P sublevels and excitation transfer to the gs are suspected to contribute to the loss.

In this work, we use tunable single mode diode lasers (DL) for sensitized absorption measurements and polarization spectroscopy in $^4$He, $^3$He, or gas mixture cells in the mbar range. A 1083$~$nm DBR DL selectively pumps atoms from the 2$^3$S level and a 707$~$nm ECDL probes populations in the 2$^3$P sublevels (see Fig.). Probe absorption signals yield rate constants for velocity-, J-, and F-changing collisions, as well as for excitation transfer between 2$^3$P and gs atoms. Results will be reported and discussed with respect to MEOP efficiency.

*T.R. Gentile et al, Rev. Mod. Phys. 89 (2017) 045004.

a, b) Computed 2$^3$P-3$^3$S line structures and Doppler broadened spectra for He isotopes; c) Detection scheme and $^4$He levels; d) Absorption signal in a mixture cell.

Choix de session parallèle Autres: Division PAMO

Primary author

Ali Dia (Laboratoire Kastler Brossel and Saint Joseph University)


Dr Pierre-Jean Nacher (Laboratoire Kastler Brossel) Prof. Marie Abboud (Saint Joseph University) Dr Geneviève Tastevin (Laboratoire Kastler Brossel)

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