The half-life of 76As

Abstract

In the course of making high-accuracy measurements of arsenic, we found that the most recently published and compiled half-life of 76 As did not agree with our data as well as the earlier accepted value. To redetermine this parameter, 76 As sources were measured on four Ge gamma detector systems, and an exponential function was fitted to the decay data by two different nonlinear least-squares methods. We obtained T 1/2 = 1.09379 days with a standard uncertainty of 0.00045 days. This result is 1.5% higher than the most recent value, but is in agreement with the older, less precise, consensus value.

Believable statements of uncertainty and believable science

“…This half-life would have led to an inaccurate INAA value for Arsenic Implant in Silicon (SRM 2134) had we used it in our measurements [21]. A redetermination of the half-life [22, 23] in agreement with the previous consensus is slowly driving out the incorrect value from tabulations of nuclear data.…”

Certification of total arsenic in blood and urine standard reference materials by radiochemical neutron activation analysis and inductively coupled plasma-mass spectrometry

“…Quantitative determination of arsenic was achieved using the 559 keV line from decay of 76 As (t 1/2 =1.09379 d ± 0.00045 d). 12 Peaks were integrated and fitted using commercial software. Sample and control yield/counting geometry corrections were determined relative to standards by comparing the 77 As count rate for each sample or control with the average 77 As count rate of the processed standards.…”

Arsenic Chemistry

“…In the arsenide niccolite (also called nickeline, NiAs), every nickel atom is surrounded by six arsenic atoms, where arsenic has a valence state of −1 and nickel is +1 (Klein, 2002), 360; (Foster, 2003), 35. The Table 2.1 Isotopes of arsenic (Audi et al, 2003;Holden, 2007;Lindstrom, Blaauw and Fleming, 2003). 75 As is the only stable arsenic isotope.…”

“…The only stable (nonradioactive) and naturally occurring isotope of arsenic is arsenic-75 ( 75 As), where each nucleus of the isotope contains 42 neutrons with the 33 protons, or a mass number of 75. Numerous artificial short-lived radioisotopes of arsenic have been produced, including excited-state isomers ((Audi et al, 2003); Table 2.1; (Holden, 2007;Lindstrom, Blaauw and Fleming, 2003)). 73 As has the longest half-life, which is 80.3 days (Holden, 2007).…”

“…73 As has the longest half-life, which is 80.3 days (Holden, 2007). The possible decay modes for radioactive arsenic isotopes are electron capture (EC), electron emission (β−), positron emission (β+), internal transition (IT), and neutron emission (ne) (Audi et al, 2003;Holden, 2007;Lindstrom, Blaauw and Fleming, 2003; Table 2.1).…”