Excitation strength

Resonance-like suppression of the higher harmonics in the response spectrum of a superparamagnetic particle is investigated. Using a nonperturbative approach, we analyze the steady processes that take place under arbitrary values of the DC (bias) and AC (excitation) strengths. The results show that the suppression effect is equally achieved on varying either noise (temperature) or force (external field intensity) or by a combination of both. In the fundamental aspect, we surmise... 

The self-energy can be renormalized further by inclusion of the diagrams in Figs. 20 d-f which can be written in terms of an effective excitation matrix element as shown in Fig. 20 g. Combining the renormalization of the energy denominator with the renormalization of the excitation strength, the self-energy is obtained in the form... 

As discussed in Sect. 5, our approximation scheme for the self-energy 2j(E) is designed for a situation where the main ionic excitation strength lies in the continuum. However, from Fig. 2516 it is obvious that this situation is not at hand in Ba because the main ionic excitation strength (in this approximation) has become concentrated to the 4dav(4d 4f P) level. The approximation will then have to be improved in typically two ways ... 

In the last section results of a matter wave interference method are presented which has been developed to probe very weak excitations at ultra-low momentum. The interference between the excitations and the condensate leads to strong density modulations after the release of the cloud, whose contrast is a heterodyne probe of the excitation strength. 

Fragmentation of the electromagnetic excitation strength in this nucleus is discussed in [99Po22]. Data for this isotope are considered in vol. LB I/18B. 

Damping coefficient Forward directivity Near field Near source Permanent translation (fling) Response spectrum Seismic ground excitation Strength reduction factor Time history... 

The first two terms describe the excitation strength from the a initial state to Gf(T[) final states. The third term is an interference term, which describes the way the a a and a- ir transition amplitudes beat against each other. In gas phase photoemission (randomly oriented molecules), one has to integrate over all possible 0 and so the interference term integrates out. 

From eq. (8.50) we see that the quantity p determines the magnitude of the transition probability, p is sometimes called the excitation strength, and for small values of p we have... 

Furthermore, if pk denotes the excitation strength for oscillator ky we have initially Pk to) = 0 and finally for ti -> oo where the atom has left the surface, the only surviving terms in (8.85) are the initial energy, the kinetic energy, and Eint, such that... 

The quantity pk entering the expression for the D-W factor is the excitation strength of mode k. It is related to the mean number of phonon quanta transferred to the mode (see exercise 8.5). The summation over k in eq. (8.133) can be carried out for some model systems (see exercise), but usually it has to be carried out numerically, since pk depends upon the frequencies, and the phonon-distribution function may not be approximated with simple models as the Debye or Einstein model [82]. However, besides this common D-W factor, there are additional temperature dependencies [68], i.e., the diffraction intensities can contain some temperature dependencies which can only be obtained by solving the phonon problem simultaneously with the diffraction problem [75, 76]. 

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