A study of the S levels and the analogue levels of P by the P(He, d)S reaction

The ³¹P(³He, d)³²S reaction has been studied with high resolution at 12 MeV bombarding energy. A detailed level scheme for ³²S has been determined up to an excitation energy of 9.5 MeV revealing several previously unobserved states. The l_p values and absolute spectroscopic factors extracted from a DWBA analysis of the experimental deuteron angular distributions have provided information on the wave functions for the T = 0 states as well as for the T = 1 isobaric analogue states of ³²P. A comparison between the present data and those of previous experiments is made, and the results are discussed in terms of existing theoretical work in this mass region. Information on Coulomb displacement and symmetry energies is also extracted.     

N2O5 reactive uptake on aqueous sulfuric acid solutions coated with branched and straight-chain insoluble organic surfactants

A flow reactor coupled to a chemical ionization mass spectrometer was used to study the reactive uptake coefficients at 273 K of N2O5 on aqueous 60 wt % sulfuric acid solutions coated with insoluble organic monolayers. Both straight-chain surfactants (1-hexadecanol, 1-octadecanol, and stearic acid) and a branched surfactant (phytanic acid) were studied. The reactive uptake coefficient decreased dramatically for straight-chain surfactants. The decrease ranged from a factor of 17 to a factor of 61 depending on the type of straight-chain surfactant. In contrast to the straight-chain data, the presence of phytanic acid did not have a significant effect on the N2O5 reactive uptake coefficient (the decrease was less than the uncertainty in the data) compared to the uncoated solution. In addition to measuring the reactive uptake coefficients, we also investigated the relationship between properties of the monolayers and the reactive uptake coefficients. The reactive uptake coefficients measured on aqueous sulfuric acid subphases showed a relationship to the surface area occupied by the surfactant molecules. However, data obtained with other subphases did not overlap with this trend.     

Particle coupling to the octupole state in 89Sr from 88Sr(p,p')88Sr analog resonances and 88Sr(d,p)89Sr

A study has been made of the six most pronounced isobaric analog resonances in the ⁸⁸Sr(p, p')⁸⁸Sr (3^?) excitation function at E_p = 7.65, 7.80, 7.92, 8.78, 9.75, and 9.90 MeV. They are believed to have a simple structure in the parent nucleus ⁸⁹Sr consisting of the lowlying positive-parity, single-neutron spectrum of ⁸⁹Sr weakly coupled to the collective 3^? state in ⁸⁸Sr. A high-resolution ⁸⁸Sr(d, p)⁸⁹Sr experiment was performed to locate small 2f and 3p admixed fragments in ⁸⁹Sr which would allow these analog resonances their entrance widths. In addition, on-resonance ⁸⁸Sr(p, p')⁸⁸Sr (3^?) angular distributions were measured in order to determine the partial waves involved in the exit channel. Results are compared to a particlephonon coupling model, and overall selectivity, strengths, and angular distributions of the (p, p') analog resonances are consistent with the above interpretation.     

The 207Pb(d,p)208Pb reaction with high resolution

The reaction ²⁰⁷Pb(d, p)²⁰⁸Pb has been studied at E_d = 18.0 MeV using the MPI Heidelberg Emperor tandem accelerator and multiple-gap spectrograph. The average resolution of 18 keV was better than previous measurements, and this, combined with the long beam exposure, allowed many finer details of the neutron particle-hole structure of ²⁰⁸Pb to be examined. In all, 45 levels were seen up to E_x = 6.3 MeV, many of which had never been seen before. A DWBA analysis of the stripping transitions angular distributions is made, and values of (2J + 1)S_ij, energy centroids, and summed strengths are given. An interesting cluster of 1i_{$\text{11}\text{2}$} and 2g_{$\text{9}\text{2}$} levels at E_x ≈ 4.2 MeV are resolved and are compared to recent isobaric analog state data. A search for weak stripping strength to known pairing vibrations in ²⁰⁸Pb gave essentially negative results and points to the need for improved ultra-resolution measurements.     

Reactive Uptake of N(2)O(5) on Aqueous H(2)SO(4) Solutions Coated with 1-Component and 2-Component Monolayers

Reactive uptake of N(2)O(5) on aqueous sulfuric acid solutions was studied in the presence of 1-component (octadecanol) and 2-component (octadecanol + phytanic acid) monolayers. In the 1-component monolayer experiments, the reactive uptake coefficient depended strongly on the molecular surface area of the surfactant. Also, the 1-component monolayer showed significant resistance to mass transfer even when the fractional surface coverage of the surfactant was less than 1. For example, a monolayer of 1-octadecanol with a fractional surface coverage of 0.75 decreased the reactive uptake coefficient by a factor of 10. This is consistent with previous studies. In the 2-component monolayer experiments, the reactive uptake coefficient depended strongly on the composition of the monolayer. When the monolayer contained only straight-chain molecules (1-octadecanol), the reactive uptake coefficient decreased by a factor of 42 due to the presence of the monolayer. However, when the monolayer contained 0.20 mole fraction of a branched surfactant (phytanic acid) the reactive uptake coefficient only decreased by a factor of 2. Hence, a small amount of branched surfactant drastically changes the overall resistance to reactive uptake. Also, our results show that the overall resistance to reactive uptake of 2-component monolayers can be predicted reasonably accurately by a model that assumes the resistances to mass transfer can be combined in parallel.     

A novel flow reactor for studying reactions on liquid surfaces coated by organic monolayers: methods, validation, and initial results

A new flow reactor has been developed that allows the study of heterogeneous kinetics on an aqueous surface coated by an organic monolayer. Computational fluid dynamics simulations have been used to determine the flow characteristics for various experimental conditions. In addition a mathematical framework has been developed to derive the true first-order wall loss rate coefficient, k(1st)(w), from the experimentally observed wall loss rate, k(obs). Validation of the new flow reactor is performed by measuring the uptake of O(3) by canola oil as a function of pressure and flow velocity and the reactive uptake coefficients of N(2)O(5) by aqueous 60 wt % and 80 wt % H(2)SO(4). Using this new flow reactor, we also determined the reactive uptake coefficient of N(2)O(5) on aqueous 80 wt % H(2)SO(4) solution coated with an 1-octadecanol (C(18)H(37)OH) monolayer. The uptake coefficient was determined as (8.1 +/- 3.2) x 10-4, which is about 2 orders of magnitude lower compared to the reactive uptake coefficient on a pure aqueous 80 wt % H(2)SO(4) solution. Our measured reactive uptake coefficient can be considered as a lower limit for the reactive uptake coefficient of aqueous aerosols coated with organic monolayers in the atmosphere, because in the atmosphere organic monolayers will likely also consist of surfactants with shorter lengths and branched structures which will have a smaller overall effect.     

Regioselective Functionalization of 7‐Azaindole by Controlled Annular Isomerism: The Directed Metalation‐Group Dance

The regioselective functionalization of 7‐azaindole by controlled annular isomerism employing a directed metalation‐group migration is reported. The N7 carbamoyl azaindoles undergo regioselective metalation and quenching with an electrophile to furnish C6‐substituted derivatives which, in the presence of a catalytic amount of ClCONR₂ promotes a carbamoyl group shift or dance from N7 to N1. A second directed metalation/electrophile quench sequence leads to 2,6‐substituted azaindoles. Optimization of the metalation conditions for C2 and C6, separately and iteratively, is presented. Using the directed metalation group dance strategy, a late‐stage deuteration of an antipsychotic drug is described. Overall, the controlled migration of the carbamoyl directing group allows multiple functionalization events of the bioactive azaindole scaffold.