Ions In Ruby Research Articles

ON THE INTENSITY OF THE ABSORPTION BANDS OF RUBY

红宝石晶体中Cr3+与六个近邻O2-组成一个有严重畸变的正八面体,因而高阶奇晶场与一阶奇晶场有相同的数量级。由于红宝石中Cr3+的格位近似保持C3v对称,T2u型的高阶场非常小,可以忽略,但T1u,A2u型高阶晶场对红宝石吸收谱强度则原则上不能予以忽视,对于Y带和U⊥带,高阶场有显著贡献,但对U‖带,所产生的强度非常小。本文考虑了格点奇对称振动对U,Y带强度的贡献,发现U‖带主要是奇振动与电子耦合产生的吸收谱。由此出发,讨论了红宝石宽带振子强度、带形等问题,得到了与实验相符合的结果。

Possibility of Optical Cooling of Ruby

The possibility of cooling by an optical process of ruby is pointed out. When Cr 3+ ions in ruby are optically pumped by photons with a given energy and emit photons with higher energies, the lattice energy can be extracted as light, so that a cooling effect appears. If some possible heating effects did not overcome this cooling effect, the temperature would be actually reduced. Cooling rates and cooling capacities are given. If we could have light input powers 10 -1 Watt or 10 -2 Watt for optical pumping, it might be possible to cool from 80°K or 20°K to temperatures below 1°K, respectively. Technical problems and possible heating effects are discussed.

Spin-Lattice Relaxation of Chromium Ions in Ruby

Measurements have been made of the spin-lattice relaxation of single chromium ions and of certain chromium-chromium pairs in ruby. Pairs whose energy levels are split by `exchange' interactions equivalent to a few degrees K relax much more rapidly than the single ions. There is some evidence that the phonons participating in the relaxation have energies equal to certain of the splittings. Modulation of the `exchange' interaction by the lattice vibrations provides a possible means of relaxation of low temperatures. In sufficiently concentrated crystals (containing at least 0.21% Cr) a rapid transfer of excitation is observed between the pairs and the single ions. The relaxation via the pairs then accounts in order of magnitude for that of the single ions. The coupling to the observed pairs is too weak to explain the concentration-dependent relaxation of the single ions in more dilute crystals.

Power Output Characteristics of a Ruby Laser

The theoretical power output of a ruby laser is examined under certain idealized operating conditions, and it is found that there are two principal regions of operation. These are the regions of strong oscillation characterized by the condition pτ2/A»hν13/σ13 and the region of saturation in which pτ3/A»hν13/σ13. Here p/A is the ``pumping'' illumination within the absorption band of ruby, τ2 is a charactersitic relaxation time of fluorescence in ruby, τ3 is a characteristic thermal relaxation time from the excited U band, ν13 is the pumping frequency, and σ13 is the cross section for interaction between pumping radiation and Cr3+ ions in ruby. Efficiency of operation is examined under two limiting conditions.

Spin-Lattice Relaxation of Pairs of Chromium Ions in Ruby

THE electron paramagnetic resonance spectrum of ruby contains many weak lines as well as those of single chromium ions. It has been established from the dependence of their intensity on the chromium concentration that most of these arise from pairs of ions. An example of the ‘pair’ spectrum is given in Fig. 1. A complete analysis is hot available, but Rimai et al. have identified the lines due to nearest-neighbour pairs, and find an antiferromagnetic exchange interaction JS 1.S 2 with J = 250 cm.−1, to be present1. These pairs are not observed at low temperatures, being then almost all in their singlet ground-state. Most of the lines, however, come from more widely separated ions, and many persist even at 1.3° K. The variation of their intensities with temperature indicates that levels separated from the ground-state by 0–15 cm.−1 are present.