Volume 15, Issue 9, 01 November 1969
Index of content:
15(1969); http://dx.doi.org/10.1063/1.1652998View Description Hide Description
Antimonyfilms in the thickness range of 50 to 250 Å prepared by vacuum evaporation on single crystal KCL substrates at room temperature show an amorphous structure, which changes readily to the crystalline form on exposure to a 40–100‐kV electron beam of moderate intensity in the electron microscope. At the nucleation stage thin films show a random orientation on crystallization, whereas thicker, nearly continuous films assume a single crystalline orientation, with (111)metal‖(001)KCl.
15(1969); http://dx.doi.org/10.1063/1.1652999View Description Hide Description
A Mössbauer backscatter system has been designed which is capable of 130% resonance effect for a rolled foil stainless‐steel sample having an elliptical‐shaped scatter area of 6.46 in.2. This effect is a function of the surface area of the sample and the energy of the detected photon. For a sample surface area greater than 0.5 in.2, the 14.4‐keV γ ray is the most efficient. This system is significant for nondestructive testing because sampling times are decreased to minutes.
15(1969); http://dx.doi.org/10.1063/1.1653000View Description Hide Description
The power and gain capabilities of a CO2 laser are dependent upon the saturation intensity of the laser media. Saturation intensities reported in the literature range from 22 to 100 W/cm2 for seemingly similar laser discharge tube bores, currents, gas flow rates, and gas mixtures. Measurements of saturation intensities between 7.5 and 57 W/cm2 in a CO2laser amplifier indicate that this parameter is inversely related to the radius of the amplified beam. A significant increase in saturation intensity for small beam radii is attributed to diffusion of excited CO2 molecules into the beam. The experimental results are in qualitative agreement with a simplified derivation of a relation governing the saturation intensity which includes molecular diffusion. This effect can result in a serious overestimate of the capabilities of a large beam laser system designed with saturation intensities obtained from small diameter probe beams.
15(1969); http://dx.doi.org/10.1063/1.1653001View Description Hide Description
It is shown that the large differences of the peak fringe intensities in the reconstruction of time‐averaged holograms may be reduced by synchronous triangular phase modulation of the reference wave. As a by‐product, portions of the object vibrating in the same phase are revealed. Optical noise in the reconstruction is low so that the useful amplitude range in vibration analysis is significantly extended by the method described.
15(1969); http://dx.doi.org/10.1063/1.1653002View Description Hide Description
It is pointed out that published data on the compression of mode‐locked Neodymium‐glass laser pulses do not require the pulse to have a predominantly positive frequency sweep. It is shown that a random pulse carrier phase function, for example, can account for published experimental observations.
15(1969); http://dx.doi.org/10.1063/1.1653003View Description Hide Description
Measurements are reported of the frequency‐dependent complex impedance of a capacitor filled with thallium iodide vapor, photodissociated into T1+ and I− to form an electron‐free plasma. Ion concentration and collision frequency are inferred using the cold plasma dielectric constant.
15(1969); http://dx.doi.org/10.1063/1.1653004View Description Hide Description
The energy relaxation time τ e in n‐InSb for the temperature range 1.5 to 20°K has been measured directly in a heterodyne experiment at 69 GHz. A comparison of experimental values for τ e with theoretical values calculated for a degenerate electron gas yields a deformation potential constant and a piezoelectric potential constant. Values of 16.2 eV for the deformation potential constant, 1.7 × 104 d 1/2/cm for the piezoelectric constant, and 280°K for the optical phonon temperature give good agreement between experiment and theory when screening is neglected. The effects of electron degeneracy and screening upon energy relaxation are discussed.
15(1969); http://dx.doi.org/10.1063/1.1653005View Description Hide Description
Raman backscatter of a frequency‐doubled ruby laser beam by water vapor has been observed in the atmosphere, using an optical radarsystem. This return along with a Raman nitrogen return, has been used to calculate a relative water‐vapor mixing ratio profile in the atmosphere to an altitude of approximately 2 km.
15(1969); http://dx.doi.org/10.1063/1.1653006View Description Hide Description
A new type of surfacespin wave occurs in a ferromagneticfilm with an applied magnetic fieldperpendicular to the surface when the dipole and exchange energies are comparable. The surface wave propagates parallel to the surface but has a wave vector whose normal component is complex. States having a high degree of localization of the spin wave amplitude near the surfaces can occur.
15(1969); http://dx.doi.org/10.1063/1.1653007View Description Hide Description
15(1969); http://dx.doi.org/10.1063/1.1653008View Description Hide Description
Gain and saturation are investigated in a kW CO2–N2–He gas‐transport laser. The active medium flows at 35 m/sec transverse to the probe laser beam. Gain falls exponentially downstream of the excitation region with a characteristic decay distance of 7 cm, giving a decay time of approximately 2 msec. A saturation parameter of approximately 250 W cm2 is determined. This large value is due to rapid flow which sweeps the molecules through the laser beam in a time shorter than the upper state relaxation time.
15(1969); http://dx.doi.org/10.1063/1.1653009View Description Hide Description
This letter reports measurements of a new type of double alignment channeling process which simultaneously uses the ``channeling effect'' and ``blocking effect'' in a relatively simple geometry. Results for the case of 500‐keV He ions impinging on ZnO single crystals are shown to be in fair agreement with a calculation of the magnitude of this effect based on the Lindhard model of particle channeling. It is shown that the sensitivity of this measurement to the detection of atoms not on normal lattice sites is a factor of 10–50 greater than in the usual channeling experiment.
15(1969); http://dx.doi.org/10.1063/1.1653010View Description Hide Description
We have investigated the lattice disorder produced in Si by 200‐keV B implantations using the standard channeling technique. We found the disorder production strongly temperature‐dependent from about −85°C to room temperature. The annealing of the residual disorder present after such a B implantation takes place at higher temperatures. Our results indicate that the nature of the lattice disorder produced in Si by low dose ion implantation depends on the mass of the ion implanted.