Key points are not available for this paper at this time.
CONTENTS Introduction 702 I. Methods of Obtaining Negative Temperature States 703 1. Negative Temperature 703 2. Selection of Molecules in Molecular Beams by Means of Inhomogeneous Electric or Magnetic Fields 705 3. Excitation of Gas Molecules by Means of a Gas Discharge 705 4. Pulse Method of Obtaining Negative Temperatures in Semiconductors 708 5. Obtaining Negative Temperatures in Semiconductors between Levels in a Single Band (Negative Mass Amplifiers) 713 6. Obtaining Negative Temperatures by Double-Resonance Techniques 715 II. Generation and Amplification of Electromagnetic Waves by Negative Temperature Systems 718 7. Interaction of Radiation with Negative Temperature Systems 718 8. Oscillation Conditions 719 9. Resonators 721 10. Amplifiers 723 11. Quantum-Mechanical Radiation Detectors 725 Conclusion 726 Cited Literature 726
Basov et al. (1961) studied this question.