Volume 10, Issue 6, 15 March 1967
Index of content:
10(1967); http://dx.doi.org/10.1063/1.1754897View Description Hide Description
Transient pulses of 10‐MeV electrons from a linear accelerator were employed to generate stress waves in cylindrical rods of various materials. A piezoelectric accelerometer was used to determine the velocity of the induced stress wave and monitor the acceleration experienced by the end of the bar. A solution of the one‐dimensional wave equation, as altered by a specific thermoelastic term which acts as a forcing function exciting a finite bar, was obtained. The resulting qualitative agreement with the experimental findings is discussed.
10(1967); http://dx.doi.org/10.1063/1.1754898View Description Hide Description
By means of differential pressure compression tests the pressure dependence of the plastic flow stress of NaCl, KCl, and LiF is measured. The measured flow stress change can be related directly to the change in dislocation mobility. In NaCl and KCl, screw dislocation mobility is decreased under pressure by more than the shear modulus is raised; the effect is nearly zero in LiF.
10(1967); http://dx.doi.org/10.1063/1.1754899View Description Hide Description
It is shown by a rate‐equation analysis why hole‐burning effects in the absorption line of some organic dyes have been observed only when the saturable absorber is within a laser cavity. The main assumption is that the absorption line is inhomogeneously broadened and that the cross relaxation time between homogeneous components is short compared to the spontaneous decay time, but still finite. An approximate value of the cross relaxation time is also calculated.
10(1967); http://dx.doi.org/10.1063/1.1754900View Description Hide Description
Measured values of the ion radial drift velocity in an argon ion laser discharge tube are presented. The data were obtained from observation of the spontaneous emission line shapes of ion and neutral transitions from the end and from the side of the discharge. The relationship of the data to various postulated excitation processes is considered. The effect of the radial drift velocities on the observed saturation of the axial drift velocities is also discussed.
10(1967); http://dx.doi.org/10.1063/1.1754901View Description Hide Description
The stage I recovery of deformed Al amounts to approximately 4.5%, independent of the degree of deformation, but is increased by a factor of four by a large prior deformation and low temperature anneal. The recovery curves are almost linear from 20–50°K, indicating that the activation energy distribution of the defects responsible for this recovery is rather uniform. A likely explanation of the enhanced recovery is that the defects which are rearranged in stage I become disarrayed again by subsequent deformation.
10(1967); http://dx.doi.org/10.1063/1.1754902View Description Hide Description
A central tuning dip (or ``Lamb dip'') has been observed in the power output of a CW molecular laser operating at 118.6 μ. The collision broadened linewidth was calculated from the shape of the dip. From the dependence of the linewidth on pressure, a radiative lifetime of 0.64 μsec and a pressure broadening (full width) of 10 MHz/torr H2O can be estimated. Comparisons with published results for OH and H2O do not yield sufficient information to identify either as the lasing species.
10(1967); http://dx.doi.org/10.1063/1.1754903View Description Hide Description
Pulsed frequency conversion of magnetostatic modes in an axially magnetized 〈100〉 rod of yttriumirongarnet has been observed experimentally. Both upward and downward shifts from 20 MHz to 900 MHz for input frequencies between 1 and 3 GHz have been achieved. Theoretical frequency conversion and power gain are obtained from energy and momentum considerations.
10(1967); http://dx.doi.org/10.1063/1.1754904View Description Hide Description
Magnetic field‐pulsed adiabatic conversion has been observed in the extraordinary component of linearly‐polarized shear waves injected into crystals of YIG, Mn‐doped YIG, and Ga‐substituted YIG. Measurements in YIG and GaYIG of the frequency splitting between the ordinary and extraordinary waves are in good agreement with the theory presented.
10(1967); http://dx.doi.org/10.1063/1.1754905View Description Hide Description
Approximate zero‐temperature upper‐critical‐field limits H c20 (max), consistent with the recent extreme‐type‐II theory of Werthamer, Helfand, and Hohenberg (WHH), are deduced by assuming (1) an electron mean free path l 0 comparable to the interatomic spacing, (2) a spin‐orbit‐coupling‐induced spin‐flip mean free path l so=2l 0, with approximate applicability of the WHH theory in this domain, and (3) Tc and l‐independent parameters typical of present‐day high‐field superconductors. Highest H c20(max) ≈ 850 kG are obtained for high‐Tc β‐tungsten‐structure compounds.