Rotational analysis of v=1 level of n=8∼10 Rydberg states of CO by triple resonant multiphoton spectroscopy

Abstract

A detailed analysis of the rotational structure of high Rydberg states of CO converging to the ionic state is presented. These states were pumped from the 3sσB 1Σ+ state using triple resonant multiphoton excitation. The observed states were n=8∼10 of the s-, p-, d-, and f-Rydberg states in the vibrational levels with v=1. The observed spectra were rotationally well resolved and the term values, the quantum defects, and the rotational constants were obtained for these states. p- and f-Rydberg states were described by the Hund’s coupling case (d). On the other hand, only the σ component was observed for the d-Rydberg states and its linewidth was very broad. For the nf-Rydberg state, the long range force model was used to obtain the ionization potential of CO(v=1), the polarizability and the quadrupole moment of the CO+ core. The mixing among Rydberg states seems to be large, as suggested by anomalous values of the rotational constants for several states. In particular, in the nf-Rydberg states, a rotational branch that should not appear for a pure Rydberg state was observed, and was explained by mixing with nearby (n+1)s-Rydberg states.