Soft-x-ray excitation involving C $1s$ electrons in CO and acetone, ${\left(\mathrm{C}{\mathrm{H}}_3\right)}_2$CO, is found to result in ionic fragmentation of the original molecule. The fragmentation pattern changes whether the C $1s$ electron gets ionized or excited into a Rydberg-line orbital or into an antibonding ${\pi }^{*}$ molecular orbital. Moreover, the fragmentation occurs specifically around the site of the carbon atom where the optical excitation takes place. Based on these observations one might consider the use of tunable soft x rays to stimulate chemical reactions or to selectively break large organic molecules.

• Received 28 January 1983

DOI:https://doi.org/10.1103/PhysRevLett.50.1038