Electronic excitation spectra of $Cl2O,$ ClOOCl, and $F2O:$ A SAC-CI study

The SAC-CI method was applied to the electronic excitation spectra of $Cl2O,$ ClOOCl, and $F2O.$ The ensuing theoretical spectra have well reproduced the experimental spectra for $Cl2O$ and $Cl2O2$ and detailed characterizations of the peaks and structures were given by calculating the oscillator strength, second moment, and dipole moment for each state. For the UV region of $Cl2O,$ the observed peaks were assigned to the valence excited states in agreement with the previous theoretical studies. For the VUV region, in the present study we have proposed the first theoretical assignments. Both valence and Rydberg excited states were calculated in this energy region, some of which resulted different from the experimental assignments. For $Cl2O2,$ the broad band of the experimental spectrum was mainly attributed to one intense peak due to the 3B state. The theoretical spectrum above 6 eV was proposed, which so far has not been addressed and clarified before. The excitation spectrum of $F2O$ up to about 13.0 eV was calculated and compared with the previous theoretical study. The shape and main features of the calculated spectrum was found to be very similar to that of $Cl2O,$ and the valence and Rydberg excited states were clearly discriminated.