Excited-pair ionization

Unfortunately the interesting consequence of a CC bond shortening upon excitation or ionization does not follow immediately. Indeed, in the ethane positive ion at least, as calculations by Pople and collaborators have shown, the ordering of the parent molecule both orbitals are very close. 

The density of excitation and ionization is not necessarily the same for all radiation qualities. For example, it is greater along the track of an a-par-ticle than for an electron track. For a primary-recoil electron produced by Co 7-rays in water, the distance between successive ionizations is about 1000 A. TTie ionized track is, therefore, sparse. At each point of ionization, secondary electrons give rise to further ionizations, forming a group of ion-pairs. In contrast, a-particles form a continuous track as a result of overlapping between the spheres of ionization. 

The present article will be restricted to discussions of dissociative recombination and resonant ion-pair formation (process 3). Dissociative excitation, dissociative ionization, and electron impact detachment of negative ions have been reviewed recently.The field of merged-beams experiments in atomic and molecular physics has recently been reviewed, and the reader is referred to this excellent article for a detailed discussion of the merged-beams technique. 

While fluorine atoms do, of course, have lone pairs of electrons they are so tightly bound that excitation or ionization from the MOs formed from them produce only high energy bands in both PE and UV spectra. This is also true for the MOs mainly populated in the C-F bonds. Thus in saturated molecules containing only C, H and F (except for CF4) the bands of lower energy are due to bonding (C—C and C—H) a electrons just as in paraffins. 

---