The effect of the chemical state on the decay constant $\lambda$ of the $\beta$ emitter ${}_{}{}^{77}{}_{}{}^{}\mathrm{As}$ has been investigated by means of a differential ionization chamber. The result of the measurement is $\lambda \left(\mathrm{metallic} {}_{}{}^{77}{}_{}{}^{}\mathrm{As}\right)-\lambda \left({\mathrm{Ag}}_3{}_{}{}^{77}{}_{}{}^{}\mathrm{As}{\mathrm{O}}_4\right)=(0.93\mathrm{}\pm 0.44)\times {10}^{-4\mathrm{}}\lambda$.

RADIOACTIVITY ${}_{}{}^{77}{}_{}{}^{}\mathrm{As}$, measured $T_{\frac{1}{2}}$, double ionization chamber, chemical effect.

• Received 19 January 1981

DOI:https://doi.org/10.1103/PhysRevC.23.2377