Lifetime and population of the 2S state in muonic protium and deuterium

TL;DR

This study measures the lifetimes and populations of the 2S metastable state in muonic protium and deuterium, providing new precision data and evidence for radiative deexcitation and muonic molecule formation.

Contribution

It offers improved measurements of 2S state lifetimes and populations in muonic protium and deuterium, including evidence for radiative deexcitation of long-lived states.

Findings

Short-lived 2S component in muonic deuterium has a lifetime of ~138 ns.

Approximately 3.1% of muons form 2S states in muonic deuterium.

Evidence for radiative deexcitation of long-lived 2S states with a lifetime of ~1.15 μs.

Abstract

Radiative deexcitation (RD) of the metastable 2S state of muonic protium and deuterium atoms has been observed. In muonic protium, we improve the precision on lifetime and population (formation probability) values for the short-lived {\mu}p(2S) component, and give an upper limit for RD of long-lived {\mu}p(2S) atoms. In muonic deuterium at 1 hPa, 3.1 +-0.3 % of all stopped muons form {\mu}d(2S) atoms. The short-lived 2S component has a population of 1.35 +0.57 -0.33 % and a lifetime of {\tau}_short({\mu}d) = 138 +32 -34 ns. We see evidence for RD of long-lived {\mu}d(2S) with a lifetime of {\tau}_long({\mu}d) = 1.15 +0.75 -0.53 {\mu}s. This is interpreted as formation and decay of excited muonic molecules.