ROTATIONAL ANALYSIS OF THE $A^{3}\Pi(1)-X^{1}\Sigma^{+}$ SYSTEM OF IC1 IN EMISSION AND IN ABSORPTION

$^{1}$E. Hulthen et al. Arkiv Fysik, 14, 31 (1958); ibid 18, 479 (1960). $^{2}$D. L. Albritton, A. L, Schmeltekopf and R. N. Zare, J. Mol. Spectrosc. 67, 132 (1977).""Author Institution: Department of Chemistry, Dalhousie UniversityDetailed rotational analyses have been made of the $A^{3}\Pi(1) \leftrightarrow X^{1}\Sigma^{+}$ system of ICl, both in emission and absorption- The A $\rightarrow$ X emission system was excited by recombination of ground state $I(^{2}P_{3}/2)$ and $C1(^{2}P_{3}/2)$ atoms in a flow system at total pressures near 2 Torr. Ten bands with $0\leq v^{\prime}\leq 2$ and $6\leq v^{\prime\prime}\leq 9$ of $I^{35}C1$ 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 $I^{35}C1$ with $3\leq v^{\prime}\leq 8$ and $2\leq v^{\prime\prime}\leq 5$ were analyzed. The present data and those obtained by refitting the precisely measured wavenumbers from the absorption spectrum at shorter $wavelengths^{1}$ were $merged^{2}$ to provide a self-consistent and extensive set of molecular constants for both the $A^{3}\Pi(1)$ and $X^{1}\Sigma^{+}$ states. The RKR turning points for these states and the Franck-Condon factors for the A - X system have been calculated