The infrared fundamental band and the five strongest near-infrared and visible electronic bands of gaseous oxygen were studied from 90 to 115 K with path lengths up to 140 m in two low-temperature multiple-traversal absorption cells. The profile of the fundamental band is in good agreement with the theory of quadrupole-induced absorption except for a low-intensity residual in the Q-branch region. Although the electronic bands are less amenable to complete analysis, the general validity of a Boltzmann relation in their intensity distributions confirms their collision-induced nature. The temperature variation of the integrated band intensities is indicative of quadrupole induction for the fundamental and of overlap induction for the electronic bands; a somewhat too sharp rise at low temperatures may be due to the neglect of the quadrupole–quadrupole coupling in evaluating the pair distribution function.
The collision-induced rotation–vibration fundamental and first overtone bands of oxygen and nitrogen have been observed in the pure gas at pressures of a few atmospheres, and in mixtures of these gases with argon at pressures of a few tens of atmospheres. From the integrated intensities of the bands it is possible to deduce a value for the first derivative of the quadrupole moment with respect to internuclear distance; we find that |Q′| = 1.6ea0 for oxygen, and |Q′| = 0.95ea0 for nitrogen.
