Paraelectric Resonance ofAg+in RbCl

Abstract

8To take into account the fact that phonon branches are not strictly Debye-like also leads to a temperature dependence of the second-sound velocity. Numerical evaluation of this temperature dependence by R. J. Hardy and S. S. Jaswal [Phys. Rev. 3, 1440(1971]for NaF and B.J. Bennett [Solid State Commun. 8, 65 (1970)] for raregas solids show also a decrease in the second-sound velocity with increasing temperature.However, for the case of NaF where experimental data are available, it is apparent that the temperature dependence due to the nonlinearity of the phonon spectrum is not sufficient to describe the experimental findings. The solution of Eq.{15)predicts a variation of the second-sound velocity from c& to the e&&(1+2') as the temperature increases and the system gradually moves from a purely ballistic regime into a hydrodynamic one. This agrees qualitatively and quantitatively well with the temperature dependence of this velocity found experimentally.A detailed numerical analysis of this will be published separately.The paraelectric resonance (PER) of Ag' in RbCl for frequencies 7. 3-36 GHz is reported.Assuming nearest-neighbor tunneling is dominant, the data are in agreement with the previously reported (111) orientation, and the observed dipole moment (uncorrected for local field) is 4. 6 +0. 1 D. Assuming a Lorentz local-field correction, this result can be interpreted as a charge e displaced approximately 0. 5 )i along a (ill) direction. The distortion of the PER line as a result of a large linewidth is discussed using a simple model, and the observed line shape at low frequencies is explained. An upper limit to the zero-field splitting is found to be 3.0 GHz.

Achievements and Current, Problems of Solid-State Radiospectroscopy

“…Новым направлением является исследование сходных явлений в жидких кристаллах 30 , играющих, как известно, большую роль в биологически важ-ных системах и находящих в последнее время все более широкое применение в технике (см., например, 31 ). Новые перспективы открывает недавно возникший метод параэлектрического резонанса (ПЭР), позволяющий изучать спектры примесных центров, обладающих постоянными электрическим дипольным моментом (например, ОН~, Li + , Ag + в КС1) в диапазоне СВЧ 32 . Расщепление уровней параэлектрического центра во внутрикри-сталлическом поле обусловлено туннелированием дипольного момента между эквива-лентными равновесными ориентациями и обычно имеет порядок нескольких см- 1 .…”

R-factor mediated resistance to ultraviolet light

“…This indicates that the plasmid mechanism of ultraviolet protection can act independently of host cell recombination repair. Bridges (1972) proposed a third repair pathway which he termed reinitiation recovery. He suggested that "UV-stalled" DNA replication forks are removed by enzymes of both the recombination and excision repair pathways, and that chromosome replication is then reinitiated at the origin.…”