Controlling Absorption of Gamma Radiation via Nuclear Level Anticrossing

A significant reduction of absorption for single gamma photons has been experimentally observed by studying Mössbauer spectra of ${}^{\mathrm{57}}\mathrm{F}\mathrm{e}$ in a ${\mathrm{F}\mathrm{e}\mathrm{C}\mathrm{O}}_3$ crystal. The experimental results have been explained in terms of a quantum interference effect involving nuclear level anticrossing due to the presence of a combined magnetic dipole and electric quadrupole interaction.

Figure 1

Observed Mössbauer spectra (dots) from a single crystal of ${\mathrm{F}\mathrm{e}\mathrm{C}\mathrm{O}}_3$ in the (a) perpendicular and (b) parallel geometry. The solid curves are the spectra obtained when the coherence and interference effects are ignored. The inset gives the ${\chi }^2$ of all fits as a function of the hyperfine field.

Figure 2

The level structure of source and absorber.

Figure 3

(a) Static frame. Simplified level structure of level anticrossing: the misalignment component of the magnetic field (providing coupling $\Omega$ between levels $a$ and $c$) acts as a driving field in optical schemes [28]. (b) Rotating frame. The coupling static field in the rotating frame acts like an ac field with the frequency equal to transition frequency. The level scheme is resembling the $\Lambda$ scheme in optics.