The quadrupole moment of the 66 keV, 5/2? state of73As

⁷³Se was produced by proton irradiation of polycrystalline arsenic. The quadrupole interaction of the 66 keV, 5/2^? state in the daughter isotope⁷³As with the electric field gradient in the noncubic arsenic lattice was observed at room temperature by means of theγ-γ perturbed angular correlation technique. The measured angular correlation pattern is characterized by a quadrupole coupling constantv _Q =51.6 (1.3) MHz. By use of the known electric field gradient on regular lattice sites, a value of ¦Q¦=0.356(12)b is derived for the quadrupole moment of the 66 keV, 5/2^? state of⁷³As.