Motion-Induced Transition of Positronium through a Static Periodic Magnetic Field in the Sub-THz Region.

Y Nagata,T Iizuka,K Michishio,Y Nagashima,H Kikutani,F Tanaka,L Chiari

doi:10.1103/physrevlett.124.173202

Abstract

Atoms moving in a static periodic field experience a time-dependent oscillating field in their own rest frame. By tuning the frequency, an atomic transition can be induced. So far, this type of transition has been demonstrated in the EUV region or at higher frequencies by crystalline fields and in the microwave region by artificial fields. Here, we present the observation of the transition of positronium (Ps) in the sub-THz region by using an energy-tunable Ps beam with a multilayered magnetic grating. This grating produces a microsized periodic field, whose amplitude corresponds to a huge energy flux of ∼100 MW cm^{-2}, resulting in the efficient magnetic dipole transition.

Highlights

Atoms moving in a static periodic field experience a time-dependent oscillating field in their own rest frame
We present the observation of the transition of positronium (Ps) in the sub-THz region by using an energy-tunable Ps beam with a multilayered magnetic grating
The transition by a crystalline field was predicted by Okorokov theoretically in 1965 [1,2] and first demonstrated in 1978 for the 1s-2p transition in the EUV region of highly charged heavy ions [3], named “resonant coherent excitation” or “Okorokov effect.”

Summary

Published by the American Physical Society

The energy difference between them is 0.84 meV (203 GHz) and was measured by a direct method [24,25] and indirect methods [26,27,28], using microwaves or lasers far This transition is electric dipole forbidden, it can be induced by a magnetic dipole. O-Ps atoms are directed through a magnetic grating, which has a periodic structure, generating a static periodic magnetic field of period length a. The velocity spread of the Ps beam is a few percent, as estimated from the momentum recoil of the photodetachment of Ps− This effect is typically a few percent [23] and is negligible with respect to the 10% resolution

Nd:YAG laser

Findings

Experiment Fit