Dipole states

Magnetic defects can be thought of as defects in the magnetic dipole state of an atom or group of atoms compared to those of the parent structure. For instance, magnetic defects can be considered to form when magnetic ions are introduced into a nonmagnetic structure, either as substituents or as interstitials (Fig. 9.1a and 9.1b). These... 

Figure 6 also summarizes the measured binding energies for dipole states versus the molecular dipole moment which adds to the data reported in the seminal papers by Desfrancois et al. The Schermarm group has provided a comprehensive review of ground-state dipole-bound anions studied... 

From a historical perspective, the first unambiguous observation of dipole states came from the group of Kit Bowen (Johns Hopkins) in 1990, who studied the important water dimer dipole anion. The Bowen group has also studied ground state dipole-bound anions produced by electron attachment under high-pressure nozzle-jet expansion condition. They have also used photodetachment photoelectron spectroscopy to determine electron affinities for a number of the molecules shown in Figure 4. 

RNC is indebted to colleagues Jean Pierre Schermann, Charles Desfrancois, Howard Carman, Eph Klots, A1 Tuinman, and Kit Bowen for their collaboration over the years. We thank Ray Garrett for a critical reading of the manuscript and for commenting on the theory of dipole states. NIH thanks the National Science Foundation (CHE-9981945) for financial support. 

Figure 1 A molecule for a generic pcet reaction. The D and A denote electron donor and acceptor, respectively. The hydrogen bonded interface supports a proton transfer reaction. As, drawn, the hydrogen bonded interface goes from a large to a small dipole state.

Electron spectroscopic observations confirm the creation and evolution dynamics of the valence states during chemisorption. In addition to the bonding states, the nonbonding lone pair of the adsorbate, the antibonding dipole states of the host, and the electron hole of the host atom can never be neglected, which modify the physical properties of a chemisporbed surface. 

The change of work function corresponds to the bandwidth of the antibonding dipole states, which provides information about the dipole formation and H-like bond formation. Dipole formation widens the bandwidth of the antibonding states and reduces the work function H-like bond formation narrows the antibonding sub-band and restores the work function, which stabilizes the entire system. The reduced work function could be of use in the cold-cathode electron emission but the H-like bond formation effects adversely. 

H-like and C-H-like Bond formation between dipole Dipole-state annihilation work function... 

---