Hyperfine Structure of Indium Fluoride

The radiofrequency spectrum of the indium fluoride molecule, 115In19F, has been measured with a high resolution molecular beam electric resonance spectrometer. We determined the hyperfine structure in the J=1 and the J=2 rotational states of several vibrational levels under conditions of very weak external electric and magnetic fields. The ∼700 MHz electric quadrupole interaction constant of the indium nucleus changes by 0.010(1) MHz between adjacent rotational states. We looked for, but did not find, an electric hexadecapole interaction of the indium nucleus; the upper limit for the (hexadecapole) interaction constant is 2 kHz.