The ⁴¹Ar(n,y)⁴²Ar reaction

The cross-section of the thermal neutron capture 41 Ar(n,γ) 42 Ar( t 1/2 =32.9 y) reaction was measured by irradiating a 40 Ar sample at the high-flux reactor of Institut Laue-Langevin (ILL) Grenoble, France. The signature of the two-neutron capture has been observed by measuring the growth curve and identifying the 1524.6 keV γ-lines of the shorter-lived 42 K(12.4 h) β − daughter of 42 Ar. Our preliminary value of the 41 Ar(n,γ) 42 Ar thermal cross section is 240(80) mb at 25.3 meV. For the first time, direct counting of 42 Ar was performed using the ultra-high sensitivity technique of noble gas accelerator mass spectrometry (NOGAMS) at Argonne National Laboratory, USA.