We have observed the cold collision frequency shift of the 1S- 2S transition in trapped spin-polarized atomic hydrogen. We find ∆ν1S-2S = -3.8+/-0.8×10-10n Hz cm3, where n is the sample density. From this we derive the 1S- 2S s-wave triplet scattering length, a1S-2S = -1.4+/-0.3 nm, which is in fair agreement with a recent calculation. The shift provides a valuable probe of the distribution of densities in a trapped sample.
Physical Review Letters
- Pub Date:
- November 1998
- Physics - Atomic Physics
- Accepted for publication in PRL, 9 pages, 4 PostScript figures, ReVTeX. Updated connection of our measurement to theoretical work