DENSITY BEHAVIOR OF THE DOUBLE ROTATIONAL TRANSITION IN LIQUID PARAHYDROGEN

We report a detailed observation and theoretical analysis of the doubl e rotational transition S-o(0)+S-o(0) of a molecular pair in liquid hy drogen. The experiment has been performed in a wide density range at c onstant temperature T=28 K. The density behavior of the integrated int ensity has been compared with the results of a theoretical model assum ing pairwise additivity of intermolecular potential and polarizability . The calculations have been carried out using quantum-mechanical path -integral Monte Carlo simulations to determine the microscopic structu re. The importance of the short-range form of the induced anisotropy i s pointed out. A satisfactory agreement is found between theory and ex periment.