Vector impedance measurements of radial mode and its three overtones of Pb (Zr,,,3Ti,,,,)0, (PZT) disk doped with MnO in the range of X = 0.1 to 9.2 mole% have been carried out using a computer controlled impedance analyzer at the room temperature. An effective value of the Poisson's ratio (8) has been determined from the fundamental to overtones frequencies ratio which comes out to be 0.34 S 0.01. The planar coupling coefficient K, is found to be independent of the overtones and peaks at around X = 1.0 mole% whereas the dielectric constant KT, peaks at X = 0.46. The coupling coefficient K , , , elastic compliance sf,, strain constant d,, and voltage constant g3, have been determined and found to be independent of overtones. The exponent 'p' and constant 'A' of the ac conductivity -frequency power law (~( u c ) = A,fP) are 0.92 and 8.7 pS/m for X < 1.0 which jumps to 0.75 and 73.8 pS/m at X 2 1.0. The values of 'p' are less than 1, which suggests that hopping mechanism is responsible for the conduction in PZT ceramics. Large variation in the piezoelectric and dielectric parameters around X = 1.0 are due to the structural changes.

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A theory for molecular collision cross section due to quadrupole-induced dipole and dipole-induced quadrupole interactions has been developed following the Anderson—Tsao—Curnutte approach. The OCS–He, OCS–Ar, and HCl–Ar collisions are discussed. For HCl–Ar collisions, μ1q1α2 interactions have been found to be important, whereas in OCS–He and OCS–Ar collisions these are negligibly small.

A theory for the collision cross section due to first-order London dispersion forces has been developed on the basis of the Anderson—Tsao—Curnutte's theory of pressure broadening. The widths of OCS J = 1→2 line broadened by helium and argon are explained.

A theory for the molecular collision cross section due to the exchange forces has been developed here following the Anderson—Tsao—Curnutte approach. The width of pure rotational lines of HCl broadened by rare gases has been theoretically calculated using the method developed here. The experimental and theoretical collision cross sections and half-intensity half-linewidths are compared, and in most cases they agree reasonably well.