Gamma Spectroscopy of Nanometer Layers of Gadolinium in the Mode of Resonantly Enhanced Standing Neutron Waves

We have shown the feasibility of detecting gamma quanta in a neutron experiment in the mode of resonantly enhanced standing waves (RESW) from a 1 nm thick gadolinium film placed in a resonator structure consisting of a 50 nm niobium layer on a sapphire substrate and coated with a 10 nm tantalum-copper film alloy. The mass of gadolinium used in the experiment was 2 μg, which is 25 times less than that in the experiment by H. Zhang et al. (H. Zhang et al., Phys. Rev. Lett. 72, 3044 (1994)). Quantitative calculations show that the experimental conditions make it possible to detect a gamma signal at waveguide resonance from a gadolinium sample weighing 40 nanograms. Thus, RESW gamma spectrometry is a powerful method for characterizing heterostructures with ultrathin gadolinium layers. In particular, it can be used to study the kinetics of interaction of hydrogen with nanometer films in which a thin layer of gadolinium is used as a label layer.