An experimental and computational study of the double ionization of CH 3Cl, CH 2Cl 2, and CHCl 3 molecules to singlet and triplet electronic states of their dications

Abstract

Experimental and computational methods were applied to study the double ionization of the molecules CH 3Cl, CH 2Cl 2, and CHCl 3. Double-charge-transfer spectroscopy was applied to measure the double-ionization energies of the molecules. The translational energies of the negative ions generated when fast-moving singly charged positive projectile ions acquire two electrons in collisions with the molecules provides information on the states of the dications populated. The use of H +, OH +, and F + projectile ions allowed transitions to singlet and triplet electronic states of the dications to be studied. Double-ionization energies to those states were calculated using the second order algebraic diagrammatic construction Green’s function method. The calculated and measured values for CH 3Cl were found to be in good agreement. The computed data predicted that the density of states for CH 2Cl 2 2+ and CHCl 3 2+ were much higher than for CH 3Cl 2+. On grouping the calculated double-ionization energies to close-lying states together, however, good agreement with the measured values was evident. The combined experimental and computational study reported here thus provides a detailed understanding of the double ionization of the three molecules to singlet and triplet electronic states of their dications.