We have measured the nascent HD(v′=1, j′) product rotational distribution from the reaction D+H2(v, j) in which the H2 reagent was either thermal (v=0, j) or prepared in the level (v=1, j=1) by stimulated Raman pumping. Translationally hot D atoms were obtained by uv laser photolysis of DBr or DI. Photolysis of DBr generated D atoms with center-of-mass collision energies (Erel) of 1.04 and 0.82 eV, which corresponded to the production of ground state Br and spin–orbit-excited Br*, respectively. The Erel values for DI photolysis were 1.38 and 0.92 eV. Quantum-state-specific detection of HD was accomplished via (2+1) resonance-enhanced multiphoton ionization and time-of-flight mass spectrometry. Vibrational excitation of the H2 reagent results in substantial rotational excitation of the HD(v′=1) product and increases the reaction rate into v′=1 by about a factor of 4. Although the quantum-mechanical calculation of Blais et al. [Chem. Phys. Lett. 166, 11 (1990)] for the D+H2(v=1, j=1)→HD(v′=1, j′)+H product rotational distribution at Erel=1.02 eV is in qualitative agreement with experiment, it does not quantitatively agree with the measured distribution. Specifically, the calculated distribution is too hot by 2–3 rotational quanta, and the predicted enhancement in the v′=1 rate with reagent vibrational excitation is too large by 67%±9.

Organophosphate esters (OPEs) have been found in remote environments at unexpectedly high concentrations, but very few measurements of OPE concentrations in seawater are available, and none are available in subsurface seawater. In this study, passive polyethylene samplers (PEs) deployed on deep-water moorings in the Fram Strait and in surface waters of Canadian Arctic lakes and coastal sites were analyzed for a suite of common OPEs. Total OPEs ( ∑OPE) at deep-water sites were dominated by chlorinated OPEs, and ranged from 6.3 to 440 pg/L. Concentrations were similar in eastern and western Fram Strait. Chlorinated OPEs were also dominant in Canadian Arctic surface waters (mean concentration ranged from < DL to 4400 pg/L), while nonhalogenated alkyl/aryl-substituted OPEs remained low (1.3-55 pg/L), possibly due to the greater long-range transport potential of chlorinated OPEs. Polybrominated diphenyl ethers (PBDEs) were found at much lower concentrations than OPEs (

We have measured state-to-state integral rate constants for the reaction D+H2(v,j) →HD(v′=0,1,2;j′)+H, in which the H2 reagent was either in the ground state, H2(v=0,j), or prepared in the first excited vibrational state, H2(v=1, j=1), by stimulated Raman pumping. Translationally hot D atoms were produced via UV photolysis of DI, generating two center-of-mass collision energies corresponding to the two I atom spin–orbit states. Resonance-enhanced multiphoton ionization and time-of-flight mass spectrometry were employed to detect the nascent HD product in a quantum-state-specific manner. Two experimental geometries were used: (1) a probe-laser-induced geometry, in which the same laser both initiated the reaction, by photolysis of DI, and detected the HD and (2) an independent-photolysis-source geometry, in which photolysis of DI was carried out by an independent laser. We find that vibrational excitation of the H2 reagent results in substantial HD rotational excitation for each product vibrational state, a shift in the vibrational product state distribution such that the rates for the reaction D+H2(v=1, j=1) into HD(v′=0) and HD(v′=1) are comparable, and somewhat surprisingly, almost no change in the total rate into HD(v′=0,1,2;j′). The experimental results are consistent with a model in which internal energy is conserved, i.e., internal energy of the reagents appears as internal energy of the products, while relative translational energy of the reagents appears primarily as translation of the products. Good to excellent agreement is found between the experiment and recent quantum-mechanical scattering calculations of Neuhauser, Judson, and Kouri. Minor discrepancies persist, however, between theory and experiment for some product rotational distributions.

A fully quantal wavepacket approach to reactive scattering in which the best available H(3) potential energy surface was used enabled a comparison with experimentally determined rates for the D + H(2)(v = 1, j = 1) --> HD(v' = 0, 1, 2; j') + H reaction at significantly higher total energies (1.4 to 2.25 electron volts) than previously possible. The theoretical results are obtained over a sufficient range of conditions that a detailed simulation of the experiment was possible, thus making this a definitive comparison of experiment and theory. Good to excellent agreement is found for the vibrational branching ratios and for the rotational distributions within each product vibrational level. However, the calculated rotational distributions are slightly hotter than the experimentally measured ones. This small discrepancy is more marked for products for which a larger fraction of the total energy appears in translation. The most likely explanation for this behavior is that refinements are needed in the potential energy surface.

Tributyltin (TBT) and its degradation products were studied by introducing radiolabeled tributyltin into a 13-m3 marine enclosure (a MERL mesocosm) with near-natural water column and benthos. TBT and its degradation products were monitored for 278 days. TBT concentrations in the water column (initially 590 ± 20 ng L'1) decreased at a rate of 0.20 day'1 for 15 days and then slowed to 0.10 day'1. Most TBT was lost from the water column through biodegradation, which occurred at a rate of 0.08 day'1. Two-thirds of the degradation proceeded through debutylation to dibutyltin (DBT), which in turn degraded to monobutyltin (MBT) at ~0.04 day'1. One-third of the TBT was degraded directly to MBT. There was no evidence for degradation of MBT in the water. Another portion of the TBT removed from the water column was transported to sediments. TBT in the sediments did not appear to measurably degrade. A portion of the TBT was apparently transported rapidly to the air-water interface and then was lost from the tank.