Final-state interactions

Gray and Wozny [101, 102] later disclosed the role of quantum interference in the vibrational predissociation of He Cl2(B, v, n = 0) and Ne Cl2(B, v, = 0) using three-dimensional wave packet calculations. Their results revealed that the high / tail for the VP product distribution of Ne Cl2(B, v ) was consistent with the final-state interactions during predissociation of the complex, while the node at in the He Cl2(B, v )Av = — 1 rotational distribution could only be accounted for through interference effects. They also implemented this model in calculations of the VP from the T-shaped He I C1(B, v = 3, n = 0) intermolecular level forming He+ I C1(B, v = 2) products [101]. The calculated I C1(B, v = 2,/) product state distribution remarkably resembles the distribution obtained by our group, open circles in Fig. 12(b). 

If the interaction potential V/ depends only on R, energy cannot flow between the translational and the vibrational modes the full or half collision is elastic (no final state interaction). The resulting quantum mechanical or classical equations of motion separate in two uncoupled blocks and the motions in R and r evolve independently of each other. 

In the photodissociation of CH3I, the inelastic force —dVi/dr partly compensates the strong restoring force —dvBc/dr with the result that, relative to the pure FC limit, CH3 is generated with comparatively weak vibrational excitation during the fragmentation the final state interaction de-excites rather than excites the umbrella vibration of CH3. 

As discussed in the introduction to this chapter the final rotation of the photofragment reflects three sources overall rotation of the parent molecule, which is preserved in the electronic excitation process, internal bending or torsional motion in the electronic ground state, and final state interaction. The latter two sources have been analyzed in Sections 10.1-10.4. The influence of overall rotation will be discussed in this section. Its relative contribution increases gradually with the magnitude of the total angular momentum J and therefore it increases with the temperature of the molecular sample. As we will demonstrate below, the conversion of overall rotation of the parent molecule in the electronic ground state into... 

Strong final state interaction, on the other hand, leads to a relatively small impact of initial rotation on the final rotation of the fragment. 

Drobits, J.C. and Lester, M.I. (1988b). Evidence for final state interactions in the vibrational predissociation of ICL-Ne complexes, J. Chem. Phys. 89, 4716-4725. 

Practical approximations for t are binary-encounter operators such as U3, which do not depend on the ion coordinates. The target and ion are therefore represented by the overlap (i+ 0), which is shown by experiments described in section 11.1.2 to be small unless i+) is the ground state 0+). These approximations were made by McCarthy and Shang (1993). They represented the final-state interaction in the long-range on-shell direct amplitude of (10.50) by the factor C(t])e "° (10.38). This factor was omitted from the resonant amplitude on the basis of the semiclassical picture of the two electrons emerging at different times. 

Let us next assume a case in which the quantum energy levels ef i = 0,1,2,... and ef j = 0,1,2,... are identified at the critical region SR, beyond which these modes are approximately separated from each other. Besides, it is assumed that the levels change only adiabatically beyond SR and that the ratios of energy intervals such as ef — ef do not vary largely. For this situation to be valid, the so-called final-state interaction must be small. This is not a pathological assumption in many statistical reactions. 

Christen J. and Bimberg D. (1990), Line shapes of intersnbband and excitonic recombination in quantum wells influence of final-state interaction, statistical broadening, and momentum conservation , Phys. Rev. B 42,7213-7219. 

Another recent advance in electron-molecule resonances is their role in molecular autoionization and photoionization. Here they show up as an exit-channel effect. The increasing availability of synchrotron sources and the proliferation of high-resolution laser spectroscopic techniques are leading to expanded interest in these processes because of the necessity to interpret the resonance features for a greater variety of molecules of chemical interest. Electron-molecule shape resonances are also responsible for structure in inner-shell electron energy-loss spectra in the region around the core ionization threshold acting as a final-state interaction, the same resonances... 

The occuring of the resonance line in the 3 d emission spectra suggests an appreciable amount of overlap between the empty 5/and 3d wave functions. As a consequence, the exchange interaction between the photohole and the 5/holes can be noticeable. Then, the final-state interactions should produce a demultiplication of photoabsorption spectra, analogous to that observed in the rare earth 3 d spectra. In-... 

One can see that the agreement with the experimental data is rather good. However, at 77.5 MeV, an enhancement over the phase space distribution is clearly seen. The difference between the experimental points and the phase space distribution is shown in the inset. The observed peak lies at 3.5 0.5 MeV above the mass of 3H+n and its width is about 1 MeV. The area under the peak implies a cross section of 150 50 nb/sr and can be attributed to the 3H+n final-state interaction corresponding to transitions to the ground state of unbound 4H. A similar level has been observed in the reaction 6Li(6Li, 8B)4H [ref.9)] and in the w -induced reactions on 6Li [ref.,s)] and on 7Li [ref.7)]. The evidence for the existence of a strong resonant... 

The resulting spectrum of 140 measured in ten independent runs is shown in fig. 5. Despite the rather low number of counts, the enhancement at 53 MeV is clearly observed. We have attempted to fit the spectrum with the five-body 140+3H+ n + n+n phase space contribution (dashed line) but with little success. In order to explain the experimental data which cannot be reproduced by either five- or four-body phase space we had to include the three-body exit channel 140 + 5H + n, though neither bound nor unbound levels have been observed in the 9Be(uB, 150)5H reaction. A similar situation has appeared in the 7Li(ir, ir+)7H reaction12), where the contribution from the 7H- 5H + n + n exit channel had to be included. This fact can only be understood as a consequence of the final state interaction in the SH system with a very large width (T 10 MeV), that makes it very difficult to observe this interaction as a peak in the reactions leading directly to the 5H nucleus. 

The pairing between the two neutrons in the 5H system plays an important role. Though the spectrum of lsO shows no evidence for a sharp unbound state in the 5H system, there is a phase space contribution from the 140 + 5H n exit channel indicating a strong final state interaction with a rather large width (F 10 MeV). 

As a result of our investigations we can make up relatively simple systematics of neutron-rich hydrogen isotopes. The final state interaction in the 4H and 6H system between 3H+n and 5H + n has a narrow width (f 2 MeV) and produces relatively... 

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