Pair creation

Note that in Regimes II and III, pair-creation of defects does riot take place rather the defect population gradually dwiridles by pair-annihilation during collisions. Numerical simulations suggest that the average number of defects decreases... 

Abstract. We have studied the effects of an hypothetical initial generation made only of very massive stars (M > 100M , pair-creation SNe) on the chemical and photometric evolution of spheroidal systems. We found that the effects of Population III stars on the chemical enrichment is negligible if only one or two generations of such stars occurred, whereas they produce quite different results from the standard models if they continuously formed for a period not shorter than 0.1 Gyr. In this case, the results produced are at variance with the main observational constraints of ellipticals such as the average [< a/Fe > ] ratio in stars and the color-magnitude diagram. 

Neutron stars (NSs) are perhaps the most interesting astronomical objects from the physical point of view. They are associated with a variety of extreme phenomena and matter states for example, magnetic fields beyond the QED vacuum pair-creation limit, supranuclear densities, superfluidity, superconductivity, exotic condensates and deconfined quark matter, etc. 

The delta functions are zero unless r = r0 and t = t0, and the rate of radical pair creation is, in effect, infinitely fast. Consequently, eqn. (10) becomes... 

A more complicated situation of bimolecular steps arises if the step depends on two lattice sites l and n. Examples are reaction process (A + B —> 0 + 0), diffusion (A + 0 —> 0 + A) or a pair creation (0 + 0 -+ B + B) which is useful for the description of dissociative adsorption events. All these processes can be formulated by... 

Z. Marie, K. Popper, and J. P. Vigier, Violation of Heisenberg s uncertainty relations on individual particles within subset of gamma photons in e+e = 2y pair creation, Found. Phys. Lett. 1(4) (1988). 

That means the pair creation operator A P is expressed linearly in terms of a product of elementary particles operators... 

Direct verification of DR-mechanism of DIET was provided [21] by combining the state-selective photoexcitation of the sample and the controlled thermally induced release of electrons from electron traps (Fig.9a). In RGS, after electron-hole pair creation at selective excitation by photons with energies E>Eg, the hole may survive and be self-trapped if the electron is captured by any kind of traps [32], In solid Ar at T>2 K the main part of electron traps is not active [12], the electron-hole recombination occurs before self-trapping the holes, and, therefore, the concentration of W-band emitting centers decreases (Fig.9a). On the contrary, the heating... 

Atomic cryocrystals which are widely used as inert matrices in the matrix isolated spectroscopy become non-inert after excitation of an electronic subsystem. Local elastic and inelastic lattice deformation around trapped electronic excitations, population of antibonding electronic states during relaxation of the molecular-like centers, and excitation of the Rydberg states of guest species are the moving force of Frenkel-pairs formation in the bulk and desorption of atoms and molecules from the surface of the condensed rare gases. Even a tiny probability of exciton or electron-hole pair creation in the multiphoton processes under, e.g., laser irradiation has to be taken into account as it may considerably alter the energy relaxation pathways. 

A more appropriate spin-orbit coupling Hamiltonian can be derived if electron-positron pair creation processes are excluded right from the beginning (no-pair approximation). After projection on the positive energy states, a variationally stable Hamiltonian is obtained if one avoids expansion in reciprocal powers of c. Instead the Hamiltonian is transformed by properly chosen... 

Recent experiments determining the so-called chemicurrent [111] have provided some information on the importance of electron-hole pair excitation in adsorption processes. Using thin films deposited on n-type Si(l 1 1) as a Schottky diode device, the nonadiabatically generated electron-hole pairs upon both atomic and molecular chemisorption create the chemicurrent which can be measured [111, 112]. It has been estimated that for example in the NO adsorption on Ag one quarter of the adsorption energy is dissipated to electron-hole pairs. Adsorption-induced electron-hole pair creation has also been found for other metal substrates, such as Au, Pt, Pd, Cu, Ni and Fe, and even for semiconductors such as GaAs and Ge [112, 113]. 

The reaction of Eq. (3.6.15) is also possible in the reverse direction, even if relatively infrequent this is particle-antiparticle pair creation. This possibility is what underlies the idea of vacuum polarization and small effects, like the Lamb shift in atomic spectra. Positrons are not that rare Many radioactive nuclei decay by positron emission—for instance, sodium-22 ... 

In insulators and semiconductors, many electron-hole pairs are produced by a single core ionization event and resulting cascade. In metals, any holes in the conduction band quickly combine with electrons. For 100-eV photons incident on Si, the number is 50. Usually the hole-electron pair creation energy is about three times the material s band gap. 

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