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Potential energy curves of ground and excited states of tetra halomethanes and the negative ionsThe spectra of electronically excited states of strongly polar negative ions are discussed in terms of general features that may be predicted for such systems. The general properties are then studied through a systematic treatment of lithium halide and lithium hydride anions. Only one or two excited electronic levels exist for these systems, and the binding energies are so low that a limited number of bound rotational levels are associated with each of the excited states. For the states of lowest binding energies, abnormal rotational level spacings are demonstrated. Also, a discussion is given of the implictions for electron scattering and photodetachment studies, of the higher lying dipole states which cross over into the continuum. 3666

All molecules having dipole moments greater than 1.625 D (0.639 ea0) have positive electron affinities in the Born–Oppenheimer approximation (i.e., when the nuclei are stationary). However, when nuclear motion is treated exactly, the above sufficient condition for binding an extra electron is modified. We have determined the magnitudes of Born–Oppenheimer electron affinities which are required in order to insure that the negative ions of polar molecules (μ≳1.625 D) are still stable when the nuclei are free to move.

Laser irradiation of absorbing materials can be used to generate acoustic pulses with extremely high amplitude and short pulse duration. Such acoustic pulses can transfer energy and momentum to atomic particles on solid surfaces to cause desorption of the particles. We report experimental observations of the effect of laser-induced acoustic desorption (LIAD) of electrons from metal film surfaces and hydrogen ions from the surface of palladium saturated with hydrogen. We believe LIAD can be used as a gentle technique to transfer analyte molecules and ions into gas phase for mass analysis and for other applications.

Calculations are made of the minimum dipole moments necessary to bind an electron to a nonstationary finite electric dipole in a number of rotationally excited states. The critical moment for a given dipolar system is found to depend on the dipole length, the moment of inertia, and the rotational quantum state of the finite dipole. The properties of the dipolar system are discussed as to their implications for electron scattering by polar molecules.