Monitoring adsorption and sedimentation using evanescent-wave cavity ringdown ellipsometry.

We monitor the adsorption of Rhodamine 800, and the sedimentation of a polytetrafluoroethylene (PTFE) suspension at the surface of a fused-silica prism, by measuring both the absorption and s-p phase shift Δ of a 740 nm probe laser beam, using evanescent-wave cavity ringdown ellipsometry (EW-CRDE). The two systems demonstrate the complementary strengths of EW-CRDE, as the progress of adsorption of the Rhodamine 800 dye can only be observed sensitively via the measurement of absorption, whereas the progress of sedimentation of PTFE can only be observed sensitively via the measurement of Δ. We show that EW-CRDE provides a sensitive method for the measurement of Δ and demonstrates precision in Δ of about 10(-4) deg.

Preparation of oriented and aligned H(2) and HD by stimulated Raman pumping.

Stimulated Raman pumping has been used to prepare oriented and aligned samples of H(2)(nu=1,J=1,2,3) and HD(nu=1,J=2) under collision-free conditions using the (1,0) S(0), S(1), Q(1), Q(2), and O(3) lines. The M-sublevel anisotropies were interrogated by polarized [2+1] resonance-enhanced multiphoton ionization via the (0,1) O(2), O(3), and S(1) lines of the E,F (1)Sigma(g) (+)-X (1)Sigma(g) (+) system. The optical excitation schemes employed in this study generate highly oriented and aligned molecular ensembles. We show that the H(2)(nu=1,J=2,M=0) and H(2)(nu=1,J=2,M=2) samples retain their initial polarization for greater than 100 ns and are therefore suitable candidates for targets or projectiles in future scattering experiments.