Rotational transitions between J≤3 levels within the K=0 manifold have been observed for H2O–CO, HDO–CO, D2O–CO, H2O–13CO, HDO–13CO, and H217O–CO using the molecular beam electric resonance and Fourier transform microwave absorption techniques. ΔMJ=0→1 transitions within the J=1 level were also measured at high electric fields. A tunneling motion which exchanges the equivalent hydrogens gives rise to two states in the H2O and D2O complexes. The spectroscopic parameters for H2O–CO in the spatially symmetric tunneling state are [∼(B0) =2749.130(2)MHz, D0=20.9(2)kHz, and μa=1.055 32(2)D] and in the spatially antisymmetric state are [∼(B0) =2750.508(1)MHz, D0=20.5(1)kHz, and μa=1.033 07(1)D]. Hyperfine structure is resolved for all isotopes. The equilibrium structure of the complex has the heavy atoms approximately collinear. The water is hydrogen bonded to the carbon of CO; however the bond is nonlinear. At equilibrium, the O–H bond of water makes an angle of 11.5° with the a axis of the complex; the C2v axis of water is 64° from the a axis of the complex. The hydrogen bond length is about 2.41 Å. The barrier to exchange of the bound and free hydrogens is determined as 210(20) cm−1 (600 cal/mol) from the dipole moment differences between the symmetric and antisymmetric states. The tunneling proceeds through a saddle point, with C2v structure, with the hydrogen directed towards the CO subunit. The equilibrium tilt away from a linear hydrogen bond is in the direction opposite to the tunneling path.

No abstract

The radio frequency and microwave spectra of H2O–CO2, HDO–CO2, and D2O–CO2 have been measured by molecular beam electric resonance spectroscopy. Rotational constants, deuterium quadrupole coupling constants, and dipole moments are reported.

We present a kinetic study of the effects of NaF, NaCl, NaBr, and NaI on aqueous solutions of 5 nm silver nanoparticles. There are distinct differences between these halides, which we attribute to two competing, halide-induced processes: oxidative decomposition of the nanoparticle surfaces and aggregation of the nanoparticles. NaF essentially does not react with the nanoparticle surface, but at concentrations above about 75 mM induces aggregation, albeit erratically. NaCl reacts oxidatively at concentrations below 27 mM, but the reaction is very slow because of surface passivation. The distinct, and lower, onset of aggregation at 27 mM is explained by chloride ion forming a uniform layer, which lowers the charge on the nanoparticle surface to about 2/3 of its original value. Addition of NaI or NaBr is very different; the rate of oxidative decomposition is orders of magnitude faster than that of NaCl such that the onset of aggregation is less apparent.

The radiofrequency and microwave spectra of C2H2–H2O, C2H2–D2O, C2D2–H2O, and C2D2–D2O have been measured by molecular beam electric resonance spectroscopy. Rotational constants and dipole moments are reported. The structure is effectively planar with the acetylene hydrogen bonded to the oxygen of the water. The hydrogen-bond length and stretching force constant are calculated to be. 2.229 Å and 0.065 mdyn/Å, respectively. Considering the lone pair orbital structure of the water molecule, an equilibrium structure having the water plane tilted away from the a axis of the complex is expected. Even so, a comparison of the dipole moments for the different isotopically substituted species shows that the height of the barrier hindering an inversion motion is low enough that no vibrational levels lie below the top of the barrier in the double-minimum potential well.