The quadrupole moment of the As nucleus from molecular microwave data and calculated relativistic electric field gradients

► The new recommended value of the nuclear quadrupole moment of 75As obtained in this work is 311(2) mb. ► Calculation of electric field gradient at the As nucleus in the AsP molecule by the IOTC CCSD(T) method leads to the value −3.4134 a.u. ► There is not negligible contribution from the relativistic and change of picture effect.