Core state vibrational excitations and symmetry breaking in the CK and OK emission spectra of CO2

The CK and OK emission spectra of gaseous CO2 have been recorded in high resolution. From a Franck–Condon fit to the vibrational structure of the spectra, it is shown that C1s ionization leads to a bond length shortening of 2.0 pm, while O1s ionization mainly results in a displacement of the carbon atom of 5 pm, thereby breaking the D∞h symmetry of the molecule. The high resolution allowed the natural lifetime width of the O1s vacancy state to be determined to 0.07 eV and by the use of an accurate calibration procedure the adiabatic x-ray transition energies were determined. These energies were used to obtain accurate binding energies of the core electrons. The O1s binding energies in CO2 were determined to 297.651 and 541.07 eV, respectively.