Measurements of short-lived cosmogenic nuclides in rain samples

Extremely low activity levels of cosmic ray induced nuclides have been measured in freshly precipitated rainwater by quick chemical separation coupled with ultra low background gamma-spectrometry. The nuclides detected were S-38 (T-1/2 = 2.83 h)-Cl-38 (37.2 m), Cl-39 (55.6 m), Na-24 (14.96 h), Mg-28 (20.9 h), Be-7 (53.3 d) and Na-22 (2.602 y). The number of atoms in rain water were evaluated to be ranging from 400-1900 l(-1) for Cl-39 (n = 6, mean: 1200), 30-1500 l(-1) for Na-24 (n = 16, mean: 520), 80-600 l(-1) for Mg-28 (n = 13, mean: 260), 1(.)10(6)-4(.)10(7) l(-1) for Be-7 (n = 16, mean: 7(.)10(6)) and 2(.)10(3)-1(.)10(5) l(-1) for Na-22 (n = 9, mean: 2(.)10(4)). Measurements of activity levels and activity ratios of short-lived cosmic-ray induced short-lived nuclides will open new method to understand atmospheric processes occurred at the altitude of rain cloud.