Debye electric moment temperature

All the results confirm the fact (required by Debye s law) that the dielectric constant is a linear function of the reciprocal of the temperature. The electric moments (/x) of the molecules calculated from the slopes of the lines are in each case given under the table. 

As Stuart worked with very small densities which were determined experimentally, and in addition the values of the molecular polarization calculated from the measured values of the dielectric constants and the corresponding densities are strictly in accordance with Debye s law, the values of the electric moment obtained from the variation of the molecular polarization with temperature must be regarded as being very accurate. We should therefore expect that the results we obtained should agree with Stuart s within the range of experimental error, if the methods used are genuinely successful. 

Debye s theory on the whole in particular, the papers by Zahn Watson f, and Stuart J may be mentioned. The measurements were carried out for various temperatures the pressures and densities of the gas were chosen at random, i.e. were quite independent of each other. The electric moment [x was calculated from Debye s law... 

Some years ago, at Professor Debye s suggestion, I set up in the Zurich laboratory an apparatus by means of which the temperature variation of dielectric constants can be measured for a constant number of molecules. Various defects in the apparatus, in particular the use of ordinary brass condensers, prevented the dielectric constants being determined with the accuracy necessary for an accurate calculation of the electric moment, so that the moments could only be determined to about o i. io e.s.u. 

While much of his reputation was based on nonpolymeric accompHshments, such as demonstrated by the Debye-Huckel theory, the Debye-Scherrer x-ray diffraction technique, the Debye-Sears effect in liquids, the Debye temperature, the Debye shielding distance, the Debye frequency and the Debye unit of electric moment, his development of the hght scattering technique for the determination of the molecular weight of polymers resulted in his also being recognized as a world class polymer scientist. 

This induced moment is added to the permanent electric moment of the second molecule and Debye showed that the interaction energy between two molecules, due to this polarizability effect, is independent of temperature and takes the form ... 

Methods for determining permanent dipole moments and polarizabilities can be arbitrarily divided into two groups. The first is based on measuring bulk phase electrical properties of vapors, liquids, or solutions as functions of field strength, temperature, concentration, etc. following methods proposed by Debye and elaborated by Onsager. In the older Debye approach the isotope effects on the dielectric constant and thence the bulk polarization, AP, are plotted vs. reciprocal temperature and the isotope effect on the polarizability and permanent dipole moment recovered from the intercept and slope, respectively, using Equation 12.5. 

Solution Carbon monoxide has a small electric dipole moment (approx 0.1 Debye), which gives the molecules an energetically preferred orientation as T — 0. However, this dipole moment is so small that the preference is not appreciable until very low temperatures, and the random orientation of the molecules (the dipole has equal probability of pointing in one direction or its opposite) remains as the temperature is lowered. For a mole of CO, each molecule can point in either of two directions and there are 2Na configurations that are about equally probable. This model predicts a residual entropy of... 

Molecular quadrupole moments may be obtained directly by observing the optical birefringence induced in a gas by an electric field-gradient Exx = —Eyy <35—37 The birefringence nx -ny, like the dielectric polarization in Debye s treatment, is comprised of a temperature-independent contribution due to distortion of the molecule and an orientation term proportional to T l 35 ... 

Figure 9.36 shows the variation of the spontaneous electric polarization AP of NP/4-MPU with temperatures between 10 K and the melting point. AP amounts to about 15% of the electric polarization, which can be estimated from the volume density of molecular electric dipole moments of about 3 Debye (10 Cm). 

In the meantime Debye, who the year before had been appointed professor of theoretical physics at the University of Zurich, in 1912 introduced the idea of polar molecules , i.e., molecules with a permanent electric dipole moment (at that time a hypothesis) and worked out a theory for the macroscopic polarization in analogy with Langevin s theory of paramagnetic substances. He found, however, that the interactions in condensed matter could lead to a permanent dielectric polarization, corresponding to a susceptibility tending to infinity for a certain temperature, which he... 

In these equations, ks is the Boltzmann s constant (1.38 X 10 J K ), Tis the temperature, I is the first ionization potential (J), oo,- is the electronic polarizability (C m J ) and p is the dipole moment (p = ql) often given in Debye (1 Debye = 3.336 x 10 Cm). In the dipole moment equation q is the electric charge (C), and I is the distance between the positive and negative charge within a given molecule (m). The electronic polarizabihty is defined as the ease with which the electrons of molecules are displaced by an electric field, e.g. that created by an ion or a polar molecule. The polarizability is expressed in m V or... 

Dielectric analysis measures two fundamental characteristics of a material—permittivity e and conductivity o (or resistivity p)—as functions of time, temperature, and AC radial frequency (O. As was discussed above, permittivity and conductivity are two parameters characteristic of respective abilities of analyzed material to store electrical energy and transfer electric charge. Both of these parameters are related to molecular activity. For example, a "dielectric" is a material whose capacitive current (out of phase) exceeds its resistive (in phase) current. An "ideal dielectric" is an insulator with no free charges that is capable of storing electrical energy. The Debye Equation (Eq. 1-12) relates the relative permittivity e to a concept of material polarization density P [C/nP], or electrical dipole moment [C/m] per unit volume [m ], and the applied electric field V ... 

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