High-resolution laser spectroscopy of the A 3Π1 ← X 1Σ+ system of ICl IN 0.7 μm region

Abstract

Spectroscopic data for the $A,^{3}Pi_{1}$ and $X,^{1}Sigma^{+}$ states of I$^{35/37}$Cl have been obtained by many researchers using grating spectrometers and Fourier-transform infrared spectrometers.footnote{,J.A. Coxon, R.M. Gordon and M.A. Wickramaaratchi, J. Mol. Spectr. {bf 79} (1983) 363, 380.}$^,$footnote{,H. Hedderich P.F. Bernath and G.A. McRae J. Mol. Spectr. {bf 155} (1992) 384.} In a previous paperfootnote{,T.Yukiya, N. Nishimiya and M. Suzuki, J. Mol. Spectr. {bf 269} (2011) 193.} we reported the measurement of doppler limited electronic vib-rotational absorption lines of the $A,^{3}Pi_{1}$ $leftarrow$ $X,^{1}Sigma^{+}$ system of I$^{35/37}$Cl using a source modulation method, and new Mass-reduced Dunham coefficients were reported for the $X$-state. However, it is becoming increasingly common to analyse diatomic molecule spectroscopic data using the ``direct-potential-fit'' (DPF) method in which observed transition energies are fitted to simulated spectra generated from analyic models for the potential energy function(s). This method tends to require fewer fitting parameters than traditional Dunham analyses, as well as having more robust extrapolation properties in both the $v$ and $J$ domains. The present work combines all available previously reported data for the $A,^{3}Pi_{1}$ and $X,^{1}Sigma^{+}$ states with new measurements up to $v'=10$ in the 0.7$murm m$ region obtained with a tone burst method using a Ti:Sapphire Ring Laser (M Squared Ltd SolsTis CW with Tera scan) in the the first DPF analysis reported for this system. The results of this study and our new fully analytic potential energy functions for the $A,^{3}Pi_{1}$ and $X,^{1}Sigma^{+}$ states of ICl will be presented