Volume 10, Issue 5, 01 March 1967
Index of content:
10(1967); http://dx.doi.org/10.1063/1.1754883View Description Hide Description
Low‐energy electron diffraction observations of a single crystal of α‐alumina have revealed a reversible structural transformation on the (001) surface. The transformation is a function of the temperature of heat treatment of the alumina.
10(1967); http://dx.doi.org/10.1063/1.1754884View Description Hide Description
Reasonable quality holograms have been made of objects placed within 1 to 3 cm of the hologram plane without the need for any external reference beam. The reconstructions from such holograms, though not of high quality, are clearly recognizable and three‐dimensional.
10(1967); http://dx.doi.org/10.1063/1.1754885View Description Hide Description
Voltage‐biased superconducting weak contacts have been used as oscillating detectors to observe radio‐frequency absorption spectra including the Co59nuclear magnetic resonance in ferromagnetic cobalt. The detection is attributed to multiple quantum processes and differentiation of the dynamic I‐V characteristics. Used as a spectrometer, the point contact is shown to be a continusously tunable ultra‐low power oscillator‐detector from 0 to 3 × 108 Hz. It is likely that the frequency limit could be extended to the superconducting gap frequency.
10(1967); http://dx.doi.org/10.1063/1.1754887View Description Hide Description
Absolute frequencies of the 311‐μ and the 337‐μ transitions of the CN gas laser are measured to within a few parts in 107. This is achieved by mixing the laser frequencies with high order harmonics of a microwave signal in a silicon diode. The beat frequencies of these two transitions which falls at 73.5 GHz is also measured directly. The Zeeman effect of these two laser transitions is studied. Based on a detailed analysis, it is found that the existing identification of these transitions is inconsistent with our observations.
10(1967); http://dx.doi.org/10.1063/1.1754888View Description Hide Description
Visible three‐dimensional ultrasonic imaging of the interior and exterior of optically opaque objects has been achieved using a synthetic holographic technique at a frequency of 5 MHz. One ultrasonic hologram and the corresponding visible image are presented.
10(1967); http://dx.doi.org/10.1063/1.1754889View Description Hide Description
We report detection and measurement of the millimeter wave difference frequency between two near laser lines at 1.152 μ. The two spectral transitions, separated by 2.26 Å, oscillate in pure neon in a single laser device, producing about 150 μW total power in several longitudinal modes. The many resulting 51.3‐kmc beat frequencies have been studied by optical heterodyne techniques. A type of diode has been found which has enough microwave sensitivity and enough optical sensitivity to combine the optical detector and the microwaveheterodyne functions in a single element. The preliminary value for the difference in frequency between the and 2S 4 → 2P 7 transitions in neon at 150 mtorr is (51,360 ± 150) Mc. This value is not in agreement with the value calculated from Vol. I of Sitterly's Atomic Energy Levels (ref. 12).
10(1967); http://dx.doi.org/10.1063/1.1754890View Description Hide Description
10(1967); http://dx.doi.org/10.1063/1.1754891View Description Hide Description
Highly complex stimulated Raman scattering(SRS)spectra of hydrogen were produced by using narrow linewidth 1.058‐μ giant‐pulsed laser excitation. Results are presented which include the first reported observation of combination Raman lines whose frequencies are given by mv Q(1) + pv S(1) − vL where v Q(1), v S(1) and vL are the vibrational (4155 cm−1), rotational (587 cm−1) and laser frequency, respectively, m = 6, 7, or 9 and p = 0 or ±1. Numerous Raman lines described by the formula v = vL + mv Q(1) + nv S(0) + pv S(1), (m, n, p = 0, ±1, ±2,…), where v S(1) = 354 cm−1, were also observed.
LASER ACTION FROM TERBIUM TRIFLUOROACETYLACETONATE IN p‐DIOXANE AND ACETONITRILE AT ROOM TEMPERATURE10(1967); http://dx.doi.org/10.1063/1.1754892View Description Hide Description
Laser activity has been obtained from terbium tris (1, 1, 1‐trifluoroacetylacetonate) at room temperature in a liquid solution in acetonitrile and in p‐dioxane. Threshold pumping energy is about 1700 J. Characteristic line narrowing, spiking and beam collimation was exhibited.
10(1967); http://dx.doi.org/10.1063/1.1754893View Description Hide Description
Low‐frequency dielectric constantmeasurements vs temperature and electric field indicate that the ferroelectric transition in Pb3MgNb2O9 is second order. The quadratic electro‐optic coefficients in Pb3MgNb2O9 are approximately an order of magnitude smaller than those of KTN (KTa.65Nb.35O3); however, the electronic conduction effects and compositional inhomogeneity problems encountered in KTN are absent in Pb3MgNb2O9, thus making it a practically useful electro‐optic material.
10(1967); http://dx.doi.org/10.1063/1.1754894View Description Hide Description
Elasticsurface waves in quartz have been excited at 316 MHz by a method which seems also to be promising for even higher frequencies up to a few GHz. The temperature dependence of the absorption in quartz has been studied between 2°K and 300°K. When the quartz is immersed in liquid helium, an additional attenuation due to radiation on longitudinal waves into the fluid occurs which turns out to be noticeably higher than estimated.
THERMAL SWITCHING OF LASER EMISSION OF Er3+ AT 2.69 μ AND Tm3+ AT 1.86 μ IN MIXED CRYSTALS OF CaF2:ErF3:TmF310(1967); http://dx.doi.org/10.1063/1.1754895View Description Hide Description
Pronounced temperature‐dependent transfer of excitation from the Er3+ laser pump levels to lower levels of Er3+ was observed in CaF2:ErF3single crystals at ErF3 concentrations exceeding 12.5 wt %. Transfer of excitation from Er3+ to Tm3+ occurred when TmF3 was included as a second active constituent of the crystals. Stimulated emission of the 4 I 11/2 → 4 I 13/2 transition of Er3+ at 2.69 μ at 298°K resulted independently of Tm3+ and as a consequence of concentration quenching of emission of Er3+ from levels above 4 I 11/2. At 100°K reduced transfer of excitation to 4 I 11/2 of Er3+ occurred due to radiative emission from levels above 4 I 11/2, and laser emission of Tm3+ was detected at 1.86 μ.