Recent measurements on the oxidation of H2S in the Black Sea yielded rates that were ten times faster than expected. To determine if this increase was due to trace metals, measurements have been made on the oxidation of H2S in seawater with added transition metals. Below a concentration level of 100 nM, none of the metals except Fe2+ affect the rate of oxidation. At higher concentrations the rates increase for all the metals except Zn2+. The increase in the rates followed the order. The increase in the rates below sulfide precipitation appears to be related to the formation of MHS+ ion pairs that have a higher rate of oxidation than HS−. Only Fe2+ and Mn2+ have concentrations high enough to be effective in influencing the rate of oxidation of H2S in the waters of anoxic basins and sediments. The estimated rates of oxidation of H2S in the Black Sea using the laboratory measurements were found to be in reasonable agreement with the measured values. Since CuHS+ has a higher rate of oxidation than HS−, it cannot be used to explain the stability of H2S in oxic seawaters. A more likely choice is ZnHS+.

Photolysis quantum yields for NO2 + hu -O(3P) + NO are reported for the wavelength range 388-41 1 nm a t two temperatures (248 and 298 K). At room temperature, the quantum yield is found to be (0.93 f 0.10) from 388 to 398 nm and to decrease smoothly to a value of 0.12 a t 41 1 nm. Beyond the dissociation threshold (397.9 nm), quantum yields obtained at 248 K are found to be significantly lower than those at 298 K (by -10% at 400 nm and -50% at 41 1 nm). The observed quantum yield data beyond the thermodynamic threshold are explained quantitatively in terms of a mechanism involving both direct dissociation (through the use of internal rovibrational energy) and dissociation of excited NO, induced by collisions with the bath gas.

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Ab initio potential energy curves of CO are calculated to address a number of problems remaining in the interpretation of the experimental VUV absorption spectra. The calculations are of the type SCF MRSD-CI. We employed the aug-cc-pVQZ basis set for both carbon and oxygen, augmented with twelve diffuse functions, of s-, p-, and d-type, located on both atomic centers. We focus on the energy region 85,000 cm(-1) < E < 110,000 cm(-1) characterized by strong interactions between Rydberg and valence states. In this work we deal specifically with the (1)Sigma(+), (1)Pi, and (3)Pi states lying in this region. Some of the relevant findings are as follows: The minimum of the C'(1)Sigma(+) valence state is found 1920 cm(-1) above the value inferred from an extrapolation of experimental data. A new (1)Pi valence state, labeled E', is found to perturb strongly the (X(2)Sigma(+))3ppi E(1)Pi Rydberg state. The electrostatic perturbation of the (X(2)Sigma(+))3ppi c(3)Pi Rydberg state by the k(3)Pi valence state is confirmed. The energy position of the (A(2)Pi)3ssigma (3)Pi state, the triplet companion of the W(1)Pi Rydberg state, is predicted.

Ab initio MRD-CI electronic structure calculations were carried out on the NH ϩ cation. A basis set of DZ ϩ POL quality augmented with Rydberg and bond functions was employed, together with an extensive treatment of electron correlation. We find four new bound electronic states of NH ϩ , namely, three doublets ( 2 ⌬, 2 ⌺ ϩ , 2 ⌺ ϩ ) and one sextet ( 6 ⌸). A fifth bound electronic state, a quartet ( 4 ⌸) that was reported schematically in an early SCF study (Liu, H. P. D.; Verhaegen, G. J Chem Phys 1970, 53(2), 735), is calculated for the first time over a wide range of NOH distances. Electronic energies, potential energy curves, and spectroscopic constants are reported for these five states. Vertical and adiabatic excitation and ionization energies are reported, as well as vertical de-excitation energies for emission from the novel states to lower-lying bound states. The potential energy curve of NH 2ϩ (X 1 ⌺ ϩ ) was also calculated to aid in the discussion of a Rydberg bound state of NH ϩ . It is hoped that the information reported in this article will be helpful in guiding the experimental detection of these species.