value in planar chromatography , 1319 rod-like morphology, 1319 röntgen , 1319 root-mean-square end-to-end distance, in polymers , 1319 rotamer, 1320 rotational barrier, 1320 rotational constants, 1320 rotational correlation time, or , 1320 rotational diffusion, 1321 rotational diffusion coefficient, 1321 rotational frequency, in centrifugation , 1321 rotational relaxation time, , 1322 rotational term, , 1322 rotator phase transition, 1322 rotatory power, 1322 rotaxanes, 1322 rotenoids, 1323rotometer in atmospheric chemistry, 1323 roughness factor (rugosity) of a surface , 1324 rovibronic state, 1324 rubredoxin, 1324 ruby laser, 1324 rupture of a thin film , 1324 Rutherford backscattering (RBS), 1325