Knowledge Bank

A 3.8 meter cell which operates routinely at variable path lengths up to 230 meters and which may be cooled to $77\circ K$ will be $described.1$ The collision induced spectra are examined in several regions at a pressure of about 1 atmosphere and temperatures from $77-300\circ K$. The $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Delta g\leftarrow 3\Sigma g-$ system $(1.2\mu )$ consists of sharp features due to rotational fine structure of monomer $O2$ and a broad underlying continuum attributed to the collision induced spectra of oxygen dimers. Simultaneous transitions are observed at $0.6\mu$ in which a collision complex of two oxygens simultaneously undergo a $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Delta g\leftarrow 3\Sigma g-$ transition. The absorptions of collision induced transitions increase dramatically at temperatures near $ϵ/k\sim 100\circ K$ for oxygen. This occurs when the kinetic energy approaches the intermolecular potential energy and oxygen begins to cluster in the gas phase.