Quantum: Einstein,Bohr and the Great Debate About the Nature of Reality,by Manjit Kumar

The history of absolute measurements of gravity is mentioned and the reasons for making absolute measurements are indicated. The principles and main advantages and difficulties of the main method—reversible pendulum, free fall, symmetrical free motion—are discussed and examples of each method are described. Problems of comparison of different determinations and of estimating systematic errors are considered.     

Optical absorption and emission of LiYF4:Pr3+

The optical absorption, emission and excitation spectra of Pr³⁺ ions in LiYF₄ have been measured. Energy transfer is observed and an estimate of the energy transfer rate is made. The temperature dependence of the emission lifetimes for Pr³⁺ and Er³⁺ and the Judd-Ofelt theory were used to make this determination. The energy levels responsible for the various transitions have been assigned previously by Esterowitz et al. and the polarized optical absorption and emission data presented in this paper are in agreement with their excellent work.