We have searched for long-lived 2S muonic hydrogen (-p) in H2 gas at 0.8 atm. The state could be detected by observing delayed 1.9-keV 2P1S photons from collisionally quenched -p(2S). The observed upper limit (90% confidence level) for the fraction,f2S, of -p(2S) with lifetime 2S in the gas in the range, 100<2S<1000 ns, is f2S<2%. Our results are consistent with the view that most of the -p(2S) have kinetic energies greater than the 0.3-eV threshold for the inelastic collision -p(2S)+H2-p(2P)+H2 and hence are rapidly quenched. We have also measured the relative Lyman line intensities in muonic hydrogen and muonic helium at 0.8 atm with solid-state detectors [Ge for -He4 and Si(Li) for -p]. The results are (KKtotal)-p=0.460.06, KKtotal)-He4=0.760.04, (KKtotal)-He4=0.040.02. These results imply that about 7.5% of -p atoms cascade to the 2S state.
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics