Excitation and ionization of OCS molecules in strong UV and NIR laser fields

Abstract

Rydberg state excitation (RSE) is a highly non-linear physical phenomenon that is induced by ionization of atoms or molecules in strong femtosecond laser fields. Here we observe that both parent (OCS) and fragments (S, C, OC) of tri-atomic molecule, carbonyl sulfide, can survive strong 800 nm or 400 nm laser fields in high Rydberg states. The dependence of the parent and fragment RSE yields on the laser intensity and ellipticity is investigated in both laser fields, and the results are compared with those of the strong field ionization. Distinct different tendencies on laser intensity and ellipticity are observed for fragment RSE, comparing with the corresponding ions. The mechanisms of RSE and strong field ionization of OCS molecules in different laser fields are discussed based on the experimental results. Our study would shed some light on the strong field excitation and ionization of molecules irradiated by femtosecond NIR and UV laser fields.