Knowledge Bank

Detailed rotational analyses have been made of the $A3\Pi (1)\leftrightarrow X1\Sigma +$ system of ICl, both in emission and absorption- The A $\to$ X emission system was excited by recombination of ground state $I(2P3/2)$ and $C1(2P3/2)$ atoms in a flow system at total pressures near 2 Torr. Ten bands with $0\le v\prime \le 2$ and $6\le v\prime \prime \le 9$ of $I35C1$ were recorded photoelectrically in the range $\lambda 8000-9800 $ \AA, and were analysed to provide the first reliable rotational constants and terra values for these levels. The A $\leftarrow$ X system in absorption was photographed at high resolution using a 3.5 m Ebert spectrograph in the range$\lambda 7000-8000 $ \AA. Sixteen bands of $I35C1$ with $3\le v\prime \le 8$ and $2\le v\prime \prime \le 5$ were analyzed. The present data and those obtained by refitting the precisely measured wavenumbers from the absorption spectrum at shorter $wavelengths1$ were $merged2$ to provide a self-consistent and extensive set of molecular constants for both the $A3\Pi (1)$ and $X1\Sigma +$ states. The RKR turning points for these states and the Franck-Condon factors for the A - X system have been calculated.