Oscillator strength continuum

In this section we discuss the more important experimental results for continuum oscillator strengths measured by electron spectroscopy that have been reported up to mid 1978. The discussion is divided on the basis of target species rather than the type of experiment since this stresses the interrelation and complementary nature of many of the experiments. As the experimental work is far from complete in many cases, only a limited picture of the overall breakdown processes is available at present. In particular, a very limited amount of work has been reported for inner shells. More data are generally available for mass fragmentation (photoionization mass spectrometry) than for partial ionization cross sections (photoelectron spectroscopy). 

Fig. 8.6 Energy dependences of the continuum oscillator strengths IdW (shown...

The binary-encounter-dipole (BED) model of Kim and Rudd [31] couples the modified form of Mott cross section [32] with the Bom-Bethe theory [27]. BED requires the differential continuum oscillator strength (DOS) which is rather difficult to obtain. The simplest approximate version of BED is the binary-encounter-Bethe (BEB) [31] model, which does not need the knowledge of DOS for calculating the EISICS. 

The oscillator strength of the transition in eh, obtained by the dipole length formulation, is 1.1 the experimental value is >0.7. This overestimation seems to be common among all continuum models. No information on line shape is obtained in this simple model. 

The property of a molecule which gives the most information about the electronic continuum states is the differential oscillator strength in the continuum absorption region, which is defined by... 

Fig. 30. The total differential oscillator strength for benzene including the structure factor but neglecting any vibrational effects. The cross-hatched portion of the figure represents the transition to a continuum orbital of e2ll symmetry, while the remainder is for a transition to an elu orbital. The positions of higher ionization thresholds are indicated.

CONTINUUM OPTICAL OSCILLATOR- STRENGTH MEASUREMENTS BY ELECTRON... 

Although the oscillator strengths are dimensionless, their derivatives with respect to E are not, and units become a significant problem in continuum absorption. In cgs (electrostatic) units, equation (II.8) reads21... 

Optical Oscillator-Strength Measurements By Electron Spectroscopy E. Continuum Effects and (e,2e) Coincidence Experiments... 

Continuum Optical Oscillator-strength Measurements by Electron Spectroscopy in the Gas Phase... 

Fig. 4.3 Oscillator strength distribution from the K 4s state to the np states and ep continuum. Note that the vertical scale is logarathmic, not Unear as in Fig. 4.1. The oscillator strengths to the high np states are orders of magnitude smaller than in H.

The squared form factor is similar to the oscillator strength in that it passes smoothly across the ionization limit. If we are interested in ionization we simply sum over t and integrate over the continuum using Eq. (11.26). 

---