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Recent measurements and analyses of proton induced radiative-capture reactions in the vicinity of E p =100 keV performed at the Triangle Universities Nuclear Laboratory are used to calculate the thermonuclear reaction rates of relevance in astrophysical plasmas for the reactions: D(p, γ ) 3 He, 7 Li(p, γ 0,1 ) 8 Be, 9 Be(p, γ 0,1,2,3 ) 10 B, and 11 B(p, γ 0,1 ) 12 C. Higher energy data from previous measurements were included when possible. The Maxwellian-averaged reaction rates, obtained using numerical integration techniques, are presented in tabular form as a function of temperature. Capture to the ground and excited states are treated separately, thus allowing the determination of inverse reaction rates for specified target states. The high temperature cut-offs of the reaction rate calculations are discussed. The results are compared to those presented in the recent NACRE compilation, where appropriate, and new analytical approximations for the total reaction rates are presented in a standard form.

The previous publications have dealt with the angular momentum formalism of both linear and circularly polarized photons in ({gamma}, x) reactions on both polarized and unpolarized targets, and the inverse (capture) reactions initiated by polarized beams. In the present work, utilizing the general formalism of Welton, the authors deal with the linear polarization of the {gamma}-rays which are produced in capture reactions on unpolarized targets, including the possibility of having incident polarized spin {1/2} projectiles. These capture reactions are denoted by a({rvec x}, {rvec L})c, where {rvec x} is the incident polarized spin {1/2} projectile and {rvec L} represents the outgoing polarized {gamma}-ray. They present here the formalism in a convenient form, display a sample table of coefficients, and illustrate its use by means of several examples. A FORTRAN code will be made available for generating similar coefficients for other reactions.

Analyzing powers for the {sup 9}Be({rvec p},{gamma}){sup 10}B reaction were measured by stopping a 100 keV polarized proton beam in a {sup 9}Be target. The measured vector analyzing power is A{sub y}(90{degree})=0.18{plus_minus}0.03 for capture to the ground state, with smaller values at 90{degree} for the first three excited states. Astrophysical S factors were calculated for each of the final states using a direct capture plus resonance model which fit both the present analyzing power data and the previously reported cross section data. The calculated S factors at E{sub p}=0 keV for capture to the ground state and first three excited states were 0.25, 0.34, 0.27, and 0.10 keV b, respectively, which are considerably smaller than previously reported. The observed analyzing powers are explained, within experimental uncertainty, as arising from the interference of the E1 direct capture amplitude with the tails of nearby p-wave and s-wave resonances. {copyright} {ital 1998} {ital The American Physical Society}

Data obtained from studies of the $p(d\ensuremath{\rightarrow},\ensuremath{\gamma}{)}^{3}\mathrm{He}$ and the $d(p\ensuremath{\rightarrow},\ensuremath{\gamma}{)}^{3}\mathrm{He}$ reactions have been used to extract the transition amplitudes corresponding to $S=1/2$ (doublet) and $S=3/2$ (quartet) $M1$ radiative capture. Protons (deuterons) of 40 keV (80 keV) were stopped in ${\mathrm{D}}_{2}\mathrm{O}$ $({\mathrm{H}}_{2}\mathrm{O})$ ice targets. Angular distributions of $\ensuremath{\sigma}$, ${A}_{y},$ ${T}_{20},$ ${P}_{\ensuremath{\gamma}}$, and ${\mathrm{iT}}_{11}$ were fit simultaneously in terms of the four possible $E1$ $p$-wave capture amplitudes and the two $(S=1/2$ and $3/2)$ possible $M1$ $s$-wave capture amplitudes. The results obtained at ${E}_{\mathrm{cm}}=23.3$ keV indicate that the $S=1/2$ $M1$ capture cross section is 13.77 $\ifmmode\pm\else\textpm\fi{}$ 0.66 nb, while the $S=3/2$ $M1$ capture cross section is 6.74 $\ifmmode\pm\else\textpm\fi{}$ 0.44 nb. These results agree with the predictions of a recent three-body theoretical calculation which includes two-body currents [e.g., meson-exchange currents (MEC's)]. They also agree with the previous experimental determination of the doublet and quartet fusion rates obtained using the Wolfenstein-Gerstein effect to vary the relative population of $S=1/2$ and $3/2$ nuclear spins in the $\ensuremath{\mu}$-$p$-$d$ molecule prior to fusion.

New measurements of the analyzing powers ${A}_{y}$ and ${T}_{20}$ have been obtained for the $^{2}\mathrm{H}(d,\ensuremath{\gamma})^{4}\mathrm{H}\mathrm{e}$ reaction at a laboratory beam energy of $115\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$. A transition matrix element analysis results in a unique solution which indicates that the reaction proceeds by 55% $E2$, 29% $E1$, and 16% $M2$ radiation. These results are shown to be in good agreement with the results of a new refined resonating group model calculation. The impact of these results on the extrapolated value of the astrophysical $S$ factor for this reaction is discussed.

In 1997 the Flemish Environmental Agency (FEA) started a monitoring program "Pesticides in Rain in Flanders, Belgium". The original purpose of the monitoring program was to examine the possible occurrence of dichlorvos in rainwater and subsequent deposition. However, it was thought necessary from the beginning to monitor a wide range of pesticides. During the first year some 62 pesticides and metabolites and 9 polychlorinated biphenyls, were monitored at 4 locations. Nowadays the monitoring program has grown up to more than 100 pesticides and metabolites and 11 polychlorinated biphenyls examined at 8 different locations. Rainwater is collected continuously and samples are examined for pesticides and PCB's on a weekly basis. In agreement with other European studies pesticides are found in rainwater samples during times of application. Pesticides which are most frequently detected are [small alpha]-, [small beta]-endosulfan and endosulfan sulfate, [gamma]-HCH (lindane), dichlorvos, atrazine, diuron, DNOC, glyphosate and AMPA and isoproturon. Furthermore it was seen that most pesticides showed a deposition pattern related to local spraying operations.

The ${}^{11}\mathrm{B}(\stackrel{\ensuremath{\rightarrow}}{p},\ensuremath{\gamma}{)}^{12}\mathrm{C}$ reaction was studied by measuring the $\ensuremath{\gamma}$ rays that were produced when 80--100-keV polarized protons were stopped in a thick ${}^{11}\mathrm{B}$ target. Cross sections and vector analyzing powers at $90\ifmmode^\circ\else\textdegree\fi{}$ were determined as a function of energy for capture to the ground and first excited states of ${}^{12}\mathrm{C}.$ These analyzing powers are particularly sensitive to the interference between s- and p-wave contributions, and to the relative phase between direct and resonance amplitudes. The results were used to produce a reliable extrapolation of the astrophysical S factor at 0 keV by means of a direct-capture-plus-resonances model calculation. The value of $S(0)$ that was obtained for ${}^{11}\mathrm{B}(p,{\ensuremath{\gamma}}_{0}),$ $1.8\ifmmode\pm\else\textpm\fi{}0.4 \mathrm{keV}\mathrm{}\mathrm{b},$ is in agreement with previously determined values, but for ${}^{11}\mathrm{B}(p,{\ensuremath{\gamma}}_{1})$ the value of $S(0)$ is $3.5\ifmmode\pm\else\textpm\fi{}0.6 \mathrm{keV}\mathrm{}\mathrm{b}$ and is more than twice as large as previously determined values.

The first measurement of the ${}^{2}\mathrm{H}(\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}},n)p$ analyzing power near threshold has been performed using the High-Intensity Gamma-ray Source (HIGS) at the Duke Free-Electron Laser Laboratory. A 3.58 MeV $\ensuremath{\gamma}$-ray beam having an energy resolution of $2.5%$ and $100%$ linear polarization was incident on an active ${\mathrm{C}}_{6}{\mathrm{D}}_{12}$ target. Outgoing neutrons were detected parallel and perpendicular to the plane of $\ensuremath{\gamma}$-ray polarization at a lab angle of 150\ifmmode^\circ\else\textdegree\fi{}. The experimentally determined analyzing power provides a sensitive measurement of the relative $E1$ and $M1$ contributions to the total cross section.

We have performed a measurement of the cross section for the ${}^{4}\mathrm{He}(\ensuremath{\gamma},dd)$ reaction with photon energies between 150 and 250 MeV. Both reaction particles were detected in coincidence. We obtained absolute cross sections at six angles and two energy bins (150\char21{}190 MeV and 190\char21{}250 MeV). A Legendre polynomial fit to the angular distribution shows a ${\mathrm{sin}}^{2}\ensuremath{\theta}$ distribution which suggests the isospin-forbidden $E1$ transition. However, a transition matrix element (TME) analysis using only strictly allowed transitions shows that the angular distribution can be described by just two TMEs: $E2$ s- and d-wave absorption on the D state of ${}^{4}\mathrm{He}.$ We performed an inverse direct-capture calculation in order to determine if the D state could contribute to such a high degree to the cross section. This calculation indicates that 90% of the cross section arises from absorption on the D state but fails to reproduce the observed ${\mathrm{sin}}^{2}\ensuremath{\theta}$ angular distribution.

Measurements of the cross section, vector and tensor analyzing powers, and linear gamma-ray polarization in the radiative capture reactions $D(p,\ensuremath{\gamma}{)}^{3}\mathrm{He}$ and $p(d,\ensuremath{\gamma}{)}^{3}\mathrm{He}$ at c.m. energies in the range 0--53 keV allow the determination of the reduced matrix elements (RMEs) relevant for these transitions. From these RMEs the value of the integral which determines the Gerasimov-Drell-Hearn sum rule for ${}^{3}\mathrm{He}$ is obtained in the threshold region, corresponding to two-body breakup, and compared with the results of an ab initio microscopic three-body model calculation. The theoretical predictions for the value of this integral based on a ``nucleons-only'' assumption are an order of magnitude smaller than experiment. The discrepancy is reduced to about a factor of 2 when two-body currents are taken into account. This factor of 2 is due to an almost exact cancellation between the dominant $E1$ RMEs in the theoretical calculation. The excess $E1$ strength observed experimentally could provide useful insights into the nuclear interaction at low energies.

In order to determine the total organic carbon content in sludges and sediments a simple and inexpensive method is proposed allowing to determine directly the total organic carbon as CO2 and using only current laboratory materials.

A comparative study was carried out to determine levels of volatile halogenated hydrocarbons, especially trihalomethanes (THM) in different Belgian drinking waters, prepared from both ground and surface waters. In addition to examining raw and treated water leaving the production plants, changes in haloform concentration during transport in the distribution system were also studied. Only a slight decrease of haloform concentration after decompression in water towers and reservoirs occurred and was rapidly compensated by on going chlorination by residual free chlorine. Despite of the very different conditions used for chlorination in the plants studied, a fairly clear relation was found between total THM content in the finished waters and TOC-values of the raw waters, indicating that the primary organic load was the determining factor for haloform formation.

A comparative study of the PAH contents of the aquifers in the six main geological formations in Belgium was carried out and related to the organic carbon. Although PAH-values were very low, the highest mean values were observed in the Carboniferous limestone of Namur and Condroz, in the Neogene Sands of Campine and in some galery-type catchments. It was however not possible to evaluate fluctuations in time within a single catchment or between different catchments in the same aquifer. On the other hand, no relationship was found between PAH- and TOC-values.

On the occasion of the detection of both bis (2-chloroisopropyl) ether (BCIE) and bis (2-chloroethyl) ether (BCEE) in a polluted groundwater it has been possible to trace the source of this pollution on a distance of more than 100 km in a heavily polluted area. Furthermore direct infiltration of these pollutants to an aquifer, formerly used for drinking water preparation, could be demonstrated by determining the ratios between these compounds in both the infiltrating surface water and in the receiving groundwater. Multiple Ion Detection Mass Spectrometry has been proven an exellent procedure to trace specific pollution sources in heavily polluted water.

A study on polycyclic aromatic hydrocarbons (PAH) in rainwater was carried out over periods of at least one year at two locations in Belgium with different environments. Maximum amounts and concentrations of PAH were reached during the winter period, mainly due to household heating. This influence was also reflected in the relative proportions of the six PAH measured. For comparable periods the amounts of PAH were almost proportional to the quantity of rain. With the available data, and as most of the rainfall is coming from the same wind direction, it was not feasible to localise possible pollution sources based upon the distribution of PAH over the different windsectors, nor was it possible to identify significant differences for both sampling locations due to their different surroundings, indicating that the rain plays an important role in the transport and distribution of pollutants over a wide area. Between about 100 and 170 μg m−2 PAH and 2 to 3 g m−2 of total organic carbon content (TOC) per year were deposited by the rain, corresponding to mean concentrations of about 140 ng l−1 of PAH and 2.9 mg l−1 of TOC.