CHARACTERISTIC FEATURES IN PHOTOIONIZATION OF Cl III*

Chlorine lines have not been observed abundantly in astrophysical spectra as it is a highly reactive element and abundance is lower than those with even number of atomic number. However, they are being observed more and used for determination of physical conditions and chemical evolution processes in astronomical objects. The present study will report characteristic features of photoionization, dependent on the states, of Cl III that can impact on the line formation and hence in determination of various

quantities relevant to the object. The present study has been carried out using the state-of-the-art relativistic Breit-Pauli R-matrix method with close coupling (CC) approximation. A CC wavefunction expansion of Cl III includes 45-levels of the core ion with excitation going up to 4s from configurations $3s^23p^2$, $3s3p^3$, $3s^23p3d$, $3s^23p4s$, $3s3p^23d$, and $3p^4$. The low lying levels showed features that benchmarked those observed using Advance light Source experiment at LBNL

(Nahar et al 2023). The present report will elaborate those with other features, such as of low and high lying excited levels, of the process from a study of photoionization cross sections of 890 bound levels of Cl III with n$leq$10 and $lleq$9.