Knowledge Bank

Nuclear quadrupole hyperfine structure has been observed in the 1-0 vibration-rotation band of hydrogen iodide with a tunable semiconductor diode laser. The large mass and quadrupole moment of Iodine combine to allow J=1 splittings to be resolved with Doppler limited spectroscopy. Four lines, R(0) through P(3), were recorded in the $2200cm-1$ region. The splittings, which were clearly resolved in the R(0) and P(1) lines, agree relatively well with the microwave derived ground vibrational state splittings. The blended P(2) and P(3) lines are compared with calculated absorption profiles. Upper limits for the change in quadrupole coupling constant from the ground to first excited vibrational state will be discussed.