Screening coefficient

The coupling term, traditionally denoted by cr B (which has however nothing to do with the screening coefficient of Section 2.2), is the so-called cross-relaxation rate and is a relaxation parameters which depends exclusively on the dipolar interaction between nuclei A and B, contrary to auto-relaxation rates which are compounds of several contributions. For instance, if A is a carbon-13, the auto-relaxation rate can always be written as... 

Figure 3. Ablation parameters at 193 nm for various polymers a, rate constant k and b, screening coefficient fJ. See Table I for acronyms.

The photoablation behaviour of a number of polymers has been described with the aid of the moving interface model. The kinetics of ablation is characterized by the rate constant k and a laser beam attenuation by the desorbing products is quantified by the screening coefficient 6. The polymer structure strongly influences the ablation parameters and some general trends are inferred. The deposition rates and yields of the ablation products can also be precisely measured with the quartz crystal microbalance. The yields usually depend on fluence, wavelength, polymer structure and background pressure. 

Thus for the internal excitation, the field caused by induced currents in both shells is equivalent to that caused by currents in one shell with the screening coefficient ... 

Now using results given at the beginning of this section we will replace functions Um. oi) and Vm ct) by functions mKi mr) and m/i(mr), respectively. Taking into account that in the cylindrical system of coordinates the metric coefficient = r, we obtain expressions for reflection and screening coefficients, describing the field in the presence of one shell ... 

K of the free and occupied volumes, i = occ, f relative compressibility coefficient (Ch. 14) Debye screening coefficient (Ch. 1) isothermal liquid compressibility isothermal compressibility of the N, I phase positronium formation rate difference between values for the liquid (Z) and glassy state (g)... 

According to the proposed approximation, the expressions for the atomic factors representing electron scattering by neutral atoms can be obtained by summation of the components of the atomic factor /nzm (s) er the quantum states occupied by electrons, 4zm being a function of the screening coefficient y and the effective quantum number n. Expressions for the components of the atomic factors for K, L, and M shells are given in [10]. For the N shell, for which... 

Slater proposes an effective quantum number n = 3.7, the atomic factor can only be presented in the form of a sum with an infinite number of components. The series may be terminated if the effective quantum number for the N shell is taken as 3.5, 4.0, or 4.5. We calculated values of the atomic factor for the neutral Br atom with different values of n. The most satisfactory agreement with the theoretical form factors, calculated according to the Thomas—Fermi—Dirac model, was obtained at n — 4.5 screening coefficients proposed in [11] were used in the calculations. The equation of the atomic scattering function for the N shell in the case of a spherically symmetrical electron density distribution and n — 4.5 has the following form ... 

Here, o is the radius of the first Bohr orbit n is the effective quantum number Z is the atomic number of the element y is the screening coefficient. 

We will distinguish two similar terms here Slater-type orbitals and Slater orbitals. The latter term is reserved for special Slater-type orbitals, in which the exponent is easily computed by considering the effect of the screening of nucleus by the internal electronic shells. The screening coefficient is calculated according to the Slater rules seep. 451. 

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