Doubly charged molecular ions studied by double charge transfer spectroscopy

We have developed a double charge transfer (DCT) spectroscope to study doub ly charged molecular ions (dications). In the course of the development, DC T spectra of N-2, CO, and NO has been observed with energy resolution of ab out 0.5 eV. The spectral profiles observed have shown the Franck-Condon (FC ) behavior. We have made an effort to increase the resolution up to about 1 40 meV, which is much better than those (1-1.5 eV) reported in previous wor ks. In the present measurement, the vibrationally resolved DCT spectrum for N-2(++) could be obtained for the first time. The observed peak structures agree well with those calculated using FC: factors, differing meaningfully from the spectra taken with Auger electron spectroscopy (AES) and threshol d photoelectrons coincidence (TPEsCO) spectroscopy. The DCT spectroscopy mi ght be a powerful method to study the potential curves of short-lived dicat ions.