Scattering resonant

The central role played by the effective Hamiltonian in the resonant part of the transition operator (60) is illustrated in two model applications. 

We consider a single resonance of width T decaying into a unique channel. In the basis of the resonance 1) the effective Hamiltonian reduces to the scalar 

Here we consider a simple model of six noninferacfing resonances of zero-order energies E° = f - 1, (f = 1, 2,. .., 6) and of identical partial width Tq. The effective Hamiltonian is written as 

The matrix representation of the Hermitian part of (81) is diagonal in the basis of the discrete states i), i = 1, 2,. .., 6). The couplings between the resonances and the continuum are assumed to be identical and characterized by 

Ethr is the energy of the threshold. The density of states is constant from Ejhr to Eend- We neglect the background (V=0) and, since there is only one decay channel, T reduces to the scalar quantity 

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Mies F H 1969 Resonant scattering theory of association reactions and unimolecular decomposition. Comparison of the collision theory and the absolute rate theory J. Cham. Phys. 51 798-807... 

The partial wave decomposition of the incident-electron wave provides the basis of an especially appealing picture of strong, low-energy resonant scattering wherein the projectile electron spends a sufficient period of time in the vicinity... 

B1.24 Rutherford backscattering, resonance scattering, PIXE and forward (recoil) scattering... 

This overview covers the major teclnhques used in materials analysis with MeV ion beams Rutherford backscattering, chaimelling, resonance scattering, forward recoil scattering, PIXE and microbeams. We have not covered nuclear reaction analysis (NRA), because it applies to special incident-ion-target-atom combinations and is a topic of its own [1, 2]. 

Figure Bl.24.13. A thin film of LaCaMn03 on an LaA103 substrate is characterized for oxygen content with 3.05 MeV helium ions. The sharp peak in the backscattering signal at chaimel 160 is due to the resonance in the scattering cross section for oxygen. The solid line is a simulation that includes the resonance scattering cross section and was obtained with RUMP [3]. Data from E B Nyeanchi, National Accelerator Centre, Fame, South Africa.

A type of molecular resonance scattering can also occur from the formation of short-lived negative ions due to electron capture by molecules on surfrices. While this is frequently observed for molecules in the gas phase, it is not so important for chemisorbed molecules on metal surfaces because of extremely rapid quenching (electron transfer to the substrate) of the negative ion. Observations have been made for this scattering mechanism in several chemisorbed systems and in phys-isorbed layers, with the effects usually observed as smaU deviations of the cross section for inelastic scattering from that predicted from dipole scattering theory. 

Figure 2 Variations in the neutron scattering amplitude or scattering length as a function of the atomic weight. The irregularities arise from the superposition of resonance scattering on a slowly increasing potential scattering. For comparison the scattering amplitudes for X rays under two different conditions are shown. Unlike neutrons, the X-ray case exhibits a monotonic increase as a function of atomic weight.

El-Sayed, I.H., Huang, X. and El-Sayed, M.A. (2005) Surface plasmon resonance scattering and absorption of anti-EGFR antibody conjugated gold nanopartides in cancer diagnostics Applications in oral cancer. Nano Letters, 5, 829-834. 

Leupold et al. were the first to report on coherent nuclear resonant scattering of synchrotron radiation from the 67.41 keV level of Ni. The time evolution of the forward scattering was recorded by employing the so-called nuclear lighthouse... 

Ta foil First successful observation of nuclear resonance scattering of synchrotron radiation (NRS) with Ta... 

Atac et al. [330] reported on the use of the Mbssbauer scattering technique. They recorded Mbssbauer scattering spectra of platinum in iron, nickel, and cobalt at 29 K by counting the resonantly scattered 99 keV y-quanta. 

Nuclear Resonance Scattering Using Synchrotron Radiation (Mossbauer Spectroscopy in the Time Domain)... 

Nuclear Resonance Scattering Using Synchrotron Radiation... 

Some of the basic features of nuclear resonance scattering using synchrotron radiation (NFS and NIS) and of conventional MS are compared in Table 9.1. 

Fig. 9.1 Schematic representation of the experimental arrangement for nuclear resonant scattering, both for NIS and NFS...

The work of Wortmann et al. [65-67], Gavriliuk et al. [68, 69] and Sturhahn et al. [70] convincingly demonstrates the power of nuclear resonant scattering experiments with synchrotron radiation for high-pressure smdies of magnetism and lattice dynamics. An illustrative example was presented at the Fifth Seeheim Workshop by Wortmann [65] Fig. 9.28a shows NFS spectra of LuFe2 at 295 and... 

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