Knowledge Bank

The 0-0 band of the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Delta 6-3\Sigma 3-$ system of molecular oxygen has been examined at low temperatures using a White cell with an effective path of 30 meters. The integrated absorption coefficient at $87\circ K$ is nearly twice as large as at room temperature. This intensity anomaly may be interpreted in terms of a ``clustering'' process, which includes both bound -pairs and collision pairs, both of which are expected to increase in importance at low temperatures. From the temperature dependence of the integrated absorption coefficient, a clustering energy $\Delta E=-360$ cal./mole is found. At present it is not possible to separate the effects of bound-pairs and collision pairs, since both of these contribute to the maximum of the pair-distribution function which governs the spectroscopic intensity. A direct confirmation of bound oxygen dimers will depend on observation of fine structure corresponding to the bound-states of the intermolecular potential.