Measuring $^{241}$Am Dipole Response

TL;DR

This study investigates the magnetic dipole response of $^{241}$Am by measuring gamma energy shifts in $^{237}$Np decay under varying external magnetic fields, revealing field-dependent peak shifts specific to certain gamma energies.

Contribution

It provides the first experimental measurement of gamma peak shifts in $^{237}$Np decay due to applied magnetic fields, highlighting differences based on gamma energy and field orientation.

Findings

Gamma peak shifts are about 0.5 keV at 59.5 keV gamma energy.

Peak shifts depend on magnetic field orientation and mode (light or dark).

Shifts are absent in background data dominated by $^{238}$U decays.

Abstract

Americium ($^{241}$Am) with an unpaired proton in the F$_{5/2}$ state exhibits a significant magnetic dipole moment. The dipole can be experimentally measured with application of even modest external magnetic fields, as little as 1G, as a shifting in the energy spectrum of emitted gammas during the process of decaying to $^{237}$Np ground state. This paper looks at the shifting in the output energy peak of gammas from the decay of excited $^{237}$Np when two configurations of an external magnetic field are applied. The peak shifting, which does not appear in the background data dominated by $^{238}$U decays, differs for the two dominant gammas released at 26.3 keV and 59.5 keV. For the 59.5 keV peak: shifting is ~ 32% of 1-Energy Bin or about 0.5 keV. While for the 26.3 keV peak: shifting is ~ 15% of 1-Energy Bin or about 0.24 keV. Interestingly enough, there appears to be a shifting for the case where the field remains in a direction horizontal to the optical bench and the light is simply blocked or unblocked from entering the field, referred to as the light (sP) or dark (sD) modes.