No abstract

Both transverse and longitudinal Zeeman effects are studied of the most conspicuous red emission line (14 319 cm -1 ) of a MgO:Cr 3+ single crystal. The Zeeman patterns are examined experimentally, with a magnetic field parallel to the [001], [110] and [111] axes, with linear polarizations parallel and perpendicular to each direction of the magnetic field and with circular polarizations around the magnetic field.Comparing these patterns with those theoretically calculated under the reasonable assumptions, it is found that the line is a magnetic dipole radiation due to the h z 2 E -> t£ M2 transition of chormium ions with purely cubic environments. It is also found that the Jahn-Teller coupling of chromophoric electrons and lattice in the excited state may be ignored in explaining the Zeeman effect.

As an aid in planning a microwave-optical double resonance experiment, 1 * 2 we have examined by high-resolution optical spectroscopy the details of the sharp-line fluorescence of ruby (Cr 3+ in A1 2 0 3 ).The only transition which appears in the fluorescence of dilute ruby at 4°K is from 2 E(E) to 4 A 2 and appears at 6934 A. Selection rules for this transition have been calculated, 3 and partially verified for absorption. 4 The Zeeman levels to be discussed here are those occurring C E(E)< V 2.5| nt | _L .._i 15 L

Room-temperature visible laser action is reported in PrCl3 and PrBr3. Optical pumping directly into the upper laser level is accomplished by a wavelength-tunable dye laser. Threshold is less than 1 μJ. Superradiant laser action within physical dimensions of a few microns is generated by focusing the excitation light on the cleaved crystal surface. Use as an active element in integrated optics networks is indicated with over 106 individual lasers per square inch.

High-resolution optical absorption spectra of TbAlOg have been obtained between 1.4 and 4.2 °K, at 20°K and at 77°K. For T>4°K, all absorption lines show a triplet structure which is interpreted as arising from an interaction of each Tb ion with only two nearest neighbors. Below r=3.95°K, a temperature-dependent lineshift is observed giving a Neel temperature of 2V=3.95:t0.10 o K. Below the N€el temperature, the lineshift is proportional to (1 -T/T N )P with 0=O.32dbO.O8. After correction for dipolar interactions, we find for the interactions along the c axis 2.4 cm" 1 , and for those in the a-b plane 1.0 cm -1 . The magnetic moment of the ground state is derived as (9.0=b0.6) /*B. The absorption spectra measured as a function of the external field show evidence for metamagnetic transitions, and a critical field of 8 kOe is derived.