LAUSR

Hyperfine structures and the field effects of IBr molecule in its rovibronic ground state are theoretically studied by diagonalizing the effective Hamiltonian matrix. Perturbations of high-J levels up to 4 are taken into account when studying the hyperfine sub-levels of the J = 0 level, and thus, an 80 × 80 matrix is constructed and solved. Some of the experimentally absent molecular constants are computed using Dalton program. Our results will be helpful in the experimental investigation of manipulation and further cooling of cold IBr molecules.