Orbitofrontal cortical (OFC) and hippocampal (HPC) lesions in primates and rodents have been associated with impulsive behaviour. We showed previously that OFC- or HPC-lesioned rats chose the immediate low-reward (LR) option in preference to the delayed high-reward (HR) option, where LR and HR were associated with different spatial responses in a uniform grey T-maze. We now report that on a novel nonspatial T-maze task in which the HR and LR options are associated with patterned goal arms (black-and-white stripes vs. gray), OFC-lesioned rats did not show impulsive behaviour, choosing the delayed HR option, and were indistinguishable from controls. In contrast, HPC-lesioned rats exhibited impulsive choice in the nonspatial decision-making task, although they chose the HR option on the majority of trials when there was a 10-s delay associated with both goal arms. The previously reported impairment in OFC-lesioned rats on the spatial version of the intertemporal choice task is unlikely to reflect a general problem with spatial learning, because OFC lesions were without effect on acquisition of the standard reference memory water-maze task and spatial working memory performance (nonmatching-to-place) on the T-maze. The differential effect of OFC lesions on the two versions of the intertemporal choice task may be explained instead in terms of the putative role of OFC in using associative information to represent expected outcomes and generate predictions. The impulsivity in HPC-lesioned rats may reflect impaired temporal information processing, and emphasizes a role for the hippocampus beyond the spatial domain.

Deuterium fluoride gets born shivering Modern spectroscopic techniques can analyze collisions between gas phase molecules in exquisite detail, highlighting exactly which vibrations and rotations come into play. However, much chemistry of interest takes place in solution, where it's harder to tease out what happens. Dunning et al. applied infrared spectroscopy to study solution-phase formation of deuterium fluoride (DF) from F atoms, a longstanding test bed of gas phase dynamics. The DF product vibrated for a surprisingly long time before dissipating its energy to the surrounding solvent molecules. Science , this issue p. 530

Time-resolved studies using 100 fs laser pulses generate CN radicals photolytically in solution and probe their subsequent reaction with solvent molecules by monitoring both radical loss and product formation. The experiments follow the CN reactants by transient electronic spectroscopy at 400 nm and monitor the HCN products by transient vibrational spectroscopy near 3.07 microm. The observation that CN disappears more slowly than HCN appears shows that the two processes are decoupled kinetically and suggests that the CN radicals rapidly form two different types of complexes that have different reactivities. Electronic structure calculations find two bound complexes between CN and a typical solvent molecule (CH(2)Cl(2)) that are consistent with this picture. The more weakly bound complex is linear with CN bound to an H atom through the N atom, and the more strongly bound complex has a structure in which the CN bridges Cl and H atoms of the solvent. Fitting the transient absorption data with a kinetic model containing two uncoupled complexes reproduces the data for seven different chlorinated alkane solvents and yields rate constants for the reaction of each type of complex. Depending on the solvent, the linear complex reacts between 2.5 and 12 times faster than the bridging complex and is the primary source of the HCN reaction product. Increasing the Cl atom content of the solvents decreases the reaction rate for both complexes.

The 193-nm photodissociation of SO 2 has been studied using the resonantly enhanced multiphoton ionization of ground-state O( 3 P J ), coupled with velocity-map ion imaging. The dependence of the ion images on the linear polarization of pump and probe radiation has been used to determine the electronic angular momentum alignment of the recoiling, state-selected atoms, together with their speed distribution and translational anisotropy. The polarization data for J ) 1 and 2 have been used to estimate the state multipole moments of the O-atom electron spin and orbital angular momenta. The data suggest that both sources of O-atom electronic angular momentum are polarized. It is shown that the spin polarization could either arise from exit-channel couplings or be a manifestation of the participation of triplet states in the dissociation. The angular dependence of the potential energy in the exit channel is examined using long-range quadrupole-dipole and quadrupolequadrupole interaction terms, from which molecular-frame multipole moments of the orbital angular momentum of the recoiling O atoms have been calculated. Comparison with the experimentally derived multipole moments is used to help provide insight into the dissociation mechanism. The results are also discussed in light of similar experimental data from the photodissociation of N 2 O.

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms Abstract:Reactions between Cl atoms and propene can lead to HCl formation either by direct H abstraction or through a chloropropyl addition complex. Barring stabilizing collisions, the chloropropyl radical will either decompose to reactants or form HCl and allyl products.