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 C1s 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.