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

L. Ludhova (1, 2) , F. D. Amaro (3) , A. Antognini (4) , F. Biraben (5) , J. M. R. Cardoso (3) , C. A. N. Conde (3) , A. Dax (1, 6) , S. Dhawan (6) , L. M. P. Fernandes (3) , T. W. Haensch (4) , V. W. Hughes (6) , P. Indelicato (5) , L. Julien (5) , P. E. Knowles (2) , F. Kottmann (7) , Y. -W. Liu (8) , J. A. M. Lopes (3) , C. M. B. Monteiro (3) , F. Mulhauser (2) , F. Nez (5) , R. Pohl (1, 4) , P. Rabinowitz (9) , J. M. F. Dos Santos (3) , L. A. Schaller (2) , Catherine Schwob (5) , D. Taqqu (1) , J. F. C. A. Veloso (3)

1 PSI - Paul Scherrer Institute
2 dpuf - Département de Physique
3 Departamento de Física
4 MPQ - Max-Planck-Institut für Quantenoptik
5 LKB (Jussieu) - Laboratoire Kastler Brossel
6 Physics Department
7 Institut für Teilchenphysik,
8 Physics Department
9 Department of Chemistry

Metastable ${2S}$ muonic-hydrogen atoms undergo collisional ${2S}$-quenching, with rates which depend strongly on whether the $\mu p$ kinetic energy is above or below the ${2S}\to {2P}$ energy threshold. Above threshold, collisional ${2S} \to {2P}$ excitation followed by fast radiative ${2P} \to {1S}$ deexcitation is allowed. The corresponding short-lived $\mu p ({2S})$ component was measured at 0.6 hPa $\mathrm{H}_2$ room temperature gas pressure, with lifetime $\tau_{2S}^\mathrm{short} = 165 ^{+38}_{-29}$ ns (i.e., $\lambda_{2S}^\mathrm{quench} = 7.9 ^{+1.8}_{-1.6} \times 10^{12} \mathrm{s}^{-1}$ at liquid-hydrogen density) and population $\epsilon_{2S}^\mathrm{short} = 1.70^{+0.80}_{-0.56}$ % (per $\mu p$ atom). In addition, a value of the $\mu p$ cascade time, $T_\mathrm{cas}^{\mu p} = (37\pm5)$ ns, was found.

Mots clés: muonic atoms; metastable states

Domaines: Physique Atomique [physics.atom-ph]

L. Ludhova, F. D. Amaro, A. Antognini, F. Biraben, J. M. R. Cardoso, et al.. Muonic hydrogen cascade time and lifetime of the short-lived $2S$ state. Physical Review A : Atomic, molecular, and optical physics [1990-2015], 2007, 75 (4), pp.040501 (R). ⟨10.1103/PhysRevA.75.040501⟩. ⟨hal-00288133⟩