Isotope Effects in Dipole-Bound Anions of Acetone

Precision measurements using the Rydberg charge-exchange and electric field-detachment methods find that the dipole-bound electron affinity (EA) of acetone (${\mathrm{C}}_3{\mathrm{H}}_6\mathrm{O}$) is $55\pm 10\mu \mathrm{eV}$ greater than for deuterated acetone (${\mathrm{C}}_3{\mathrm{D}}_6\mathrm{O}$). The result agrees well with a theoretical prediction obtained with high-level electronic-structure and anharmonic vibrational calculations. The dipole moments calculated for the vibrationally averaged structures of ${\mathrm{C}}_3{\mathrm{H}}_6\mathrm{O}$ and ${\mathrm{C}}_3{\mathrm{D}}_6\mathrm{O}$ show that the isotope effect (2% reduction) on the EA of acetone is mainly due to a slight reduction (0.5%) of the average dipole moment upon deuteration.

Figure 1

Dipole-bound anion formation spectra of acetone and deuterated acetone from two-photon laser excited rubidium $ns$ and $nd$ Rydberg states.

Figure 2

Electric field-detachment profiles of acetone and deuterated acetone negative ions.

Figure 3

Electron binding energy as a function of the critical electric field. The electron binding energies and critical electric fields are taken from Ref. 6.