Muonic hydrogen cascade time and lifetime of the short-lived 2S state

Abstract

Metastable 2S muonic-hydrogen atoms undergo collisional 2S quenching, with rates which depend strongly on whether the μp kinetic energy is above or below the 2S→2P energy threshold. Above threshold, collisional 2S→2P excitation followed by fast radiative 2P→1S deexcitation is allowed. The corresponding short-lived μp (2S) component was measured at 0.6 hPa H2 room-temperature gas pressure, with lifetime τ 2S short = 165 -29 +38 ns (i.e., λ 2S quench = 7.9 -1.6 +1.8 × 1012 s-1 at liquid-hydrogen density) and population ε 2S short = 1.70 -0.56 +0.80 % (per μp atom). In addition, a value of the μp cascade time, Tcas μp = (37±5) ns, was found. © 2007 The American Physical Society.