Abstract
We have developed a small purely electrostatic ion-beam trap which may be operated in thermal equilibrium at precisely controlled temperatures down to 10 K. Thus, we avoid magnetic field induced mixing of quantum states and may effectively eliminate any influence from absorption of photons from blackbody radiation. We report the first correction-free measurement of the lifetime of the 1s2s2p {4}P{5/2}{0} level of 4He(-) yielding the high-precision result 359.0 +/- 0.7 micros. This result is an essential proof-of-principle for cryogenic electrostatic storage rings and traps for atomic and molecular physics.
Highlights
The He ground state cannot bind an additional electron to form a stable bound state
In 1955, Holøien and Midtdal [2] established theoretically that the metastable 1s2s2p 4PoJ state in HeÀ is bound with respect to the lowest excited state of neutral He, 1s2s 3Se
Due to the weak interaction with the nucleus, the wave functions of HeÀ extend to large distances, and as subtle details in atomic wave functions may control the corresponding decays, calculations of the relaxation of excited states in HeÀ are demanding and important
Summary
The He ground state cannot bind an additional electron to form a stable bound state. the HeÀ ion has been reported in beam experiments since 1925 [1]. We present the first direct high-precision measurement of the 4Po5=2 lifetime, where we have effectively eliminated all instrumental influences on the result by using a cryogenic, compact, and purely electrostatic ion-
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