Photoion-pair formation

In some cases the yield of photoion-pairs is quite high, but in other cases it is low due to competition with predissociation, yielding neutral species, and 

As the potential for an ion-pair state is Coulombic, it will support an infinite number of vibrational states and these form a Rydberg series close to the dissociation threshold. These weakly bound states appear to behave like the high- Rydberg states employed in ZEKE photoelectron spectroscopy, described in the previous section, and they have, therefore, been termed zero ion kinetic energy (ZIKE) states (Wang 

The threshold for photoion-pair production from jet-cooled H Cl has been determined as 116288.7 0.6 cm-  

This datum can be used to obtain the bond dissociation energy of HCl to higher precision than previously available, using the equation for energy balance  

---

Hu QJ, Hepburn JW (2006) Energetics and dynamics of threshold photoion-pair formation in HF/DF. J Chem Phys 124 74311... 

Ion pair formation competes with internal conversion from the S2 state in the chloranil-diphenylamine complex 78 and photoionization of 2,2 -bipyridine in aqueous solution involves multiphoton excitation of Ti and Si states.Monophotonic ionization from the vibrationally unrelaxed excited singlet state of N,N,N, N -tetraraethyl-p-phenylenediamine in acetonitrile shows ionization increases with energy in the Si state and slightly decreases for excitation around the S2 excitation energy level. 

In order to be able to calculate the ultraviolet spectra to be expected from arylarsines (Section III, B) it was necessary to have some idea of the ionization potential of the arsenic lone pair. Consequently the first ionization potentials of a number of simple arsines were determined and the results are given in Table V (495). The values were obtained by electron-impact mass spectrometry and may be greater than the adiabatic values, however, the trends should be reliable. The site of ionization is not known but it seems reasonable to assume that the electron is lost from the arsenic lone pair. The values also fit in well with qualitative chemical studies related to ease of complex formation and ease of solvolysis (174, 256). A value of 7.34 eV has been quoted for the first ionization potential of triphenylarsine (497). This value, determined from photoionization studies, is similar to that of a simple phenyl derivative so that the electron is probably being lost from the phenyl rings and not from he arsenic lone pair as maintained by Vilesuv and Zaitsev (497). 

---