Hyperfine transition induced by atomic motion above a paraffin-coated magnetic film

TL;DR

This study demonstrates hyperfine transitions in potassium-39 atoms induced by their motion through a periodic magnetic field above a magnetic film, revealing multi-quanta transition processes and suppression of surface relaxation effects.

Contribution

It provides experimental evidence of motion-induced hyperfine transitions and details the multi-quanta transition mechanism in a novel magnetic field configuration.

Findings

Transition probability increases with field oscillation frequency.

Multi-quanta transitions dominate over single-quantum processes.

Surface relaxation effects are minimized by paraffin coating.

Abstract

We measured transitions between the hyperfine levels of the electronic ground state of potassium-39 atoms (transition frequency: 460 MHz) as the atoms moved through a periodic magneto-static field produced above the magnetic-stripe domains of a magnetic film. The period length of the magnetic field was 3.8 um. The atoms were incident to the field as an impinging beam with the most probable velocity of 550 m/s and experienced a peak oscillating field of 20 mT. Unwanted spin relaxation caused by the collisions of the atoms with the film surface was suppressed by the paraffin coating on the film. We observed increasing hyperfine transition probabilities as the frequency of the field oscillations experienced by the atoms increased from 0 to 140 MHz for the atomic velocity of 550 m/s, by changing the incident angle of the atomic beam with respect to the stripe domains. Numerical calculation of the time evolution of the hyperfine states revealed that the oscillating magnetic field experienced by the atoms induced the hyperfine transitions, and the main process was not a single-quantum transition but rather multi-quanta transitions.