In-beam nuclear magnetic resonance in isomeric states

TLDR: In this article, a comprehensive description of the γ-NMR-PAD method combined with pulsed beam techniques is given, and detailed studies of the resonance behavior are performed as a function of various timing conditions, of the phase between the r.f. field and the creation time of the nuclear states, and of the amplitude of the linearly polarized r. f.f field.

Abstract: A comprehensive description is given of the γ-NMR-PAD method combined with pulsed beam techniques. Detailed studies of the resonance behaviour were performed as a function of various timing conditions, of the phase between the r.f. field and thecreation time of the nuclear states, and of the amplitude of the linearly polarized r.f. field. The following features were realized by experiments on the 20 ms state in71Ge and on the 119 μs state in78 Br, excited and oriented by nuclear reactions in liquid metallic targets: (i) The resonance behaviour was observed time-differentially, yielding accurate values of the r.f. amplitude acting at the nuclear site, and of the relaxation time. (ii) The observation of the perturbed γ-ray distribution in time windows can yield strongly structured resonances with considerably larger effects compared to time-integral resonances. The time window technique is well suited to determine the resonance point precisely, and further — in case of saturation — the relaxation time can be extracted. (iii) Absorptionand dispersion-like resonance structures were observed with fixed r.f. phases for selected time windows and phase positions, yielding the sign of the magnetic interaction and the sign of the γ-ray anisotropy. (iv) At r.f. amplitudes comparable to the static magnetic fields resonance shifts and multiple quantum effects caused by the “nonresonant” component of the r.f field were studied in γ-NMR-PAD. A comparison is given with the stroboscopic method, and some possible applications of the technique developed are discussed to observe hyperfine interactions of muons in non-metals.