Berlin 2001 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
A: Atomphysik
A 12: Posters Thursday (Ion/Atom/Molecule/Surface Scattering)
A 12.35: Poster
Donnerstag, 5. April 2001, 12:30–15:00, AT3
Enhancement of the 3He2 (a3Σu+) molecular state population by selective excitation of the 23P atomic state — •Emmanuel Courtade1, P.-J. Nacher1, C. Dedonder2, C. Jouvet2, and T Dohnalik3 — 1Laboratoire Kastler Brossel, 24 rue Lhomond, 75005 Paris - France. — 2Laboratoire de Photophysique Moléculaire, Univ. Paris Sud, 91405 Orsay Cedex - France. — 3Institute of Physics, Jagiellonian University, Ul. Reymonta 4, Krakow - Poland.
An efficient method to produce a high nuclear polarisation in a 3He gas relies on metastability exchange optical pumping (ME-OP) using the intense 23S - 23P atomic transition line at 1083 nm. Several applications require highly polarised high pressure gas. Unfortunately, the efficiency of ME-OP is known to strongly decrease for pressures exceeding a few mbar, probably due to the formation of molecular states in the helium plasma required for ME-OP. In the presence of intense 1083 nm light, one has to consider the creation of the a3Σu+ metastable molecular state from the 23P atomic state and two ground state atoms.
We report on a study of laser induced fluorescence on the a3 Σu+- e3Πg molecular line of a 3He gas in sealed glass cells. We excite at 465 nm (δv=0) with a pulsed dye laser (20 Hz, 10 µJ/pulse) and use a time-resolved detection of the fluorescence at 505 nm (δv=-1) to improve the sensitivity. The different rotational states are resolved and assigned. We have observed significant a3Σu+ population enhancement and present results for various 3He gas pressures (from 1 to 40 mbar) and intensities of the 1083 nm light (up to 200 W/cm2). We discuss the consequences of these measurements for ME-OP of 3He in this pressure range.