Non-covalent anion structures in dissociative electron attachment to some brominated biphenyls.

The present work combines experiment and theory to reveal the behavior of bromo-substituted-biphenyls after an electron attachment. We experimentally determine anion lifetimes using an electron attachment-magnetic sector mass spectrometer instrument. Branching ratios of dissociative electron attachment fragments on longer timescales are determined using the electron attachment-quadrupole mass spectrometer instrument. In all cases, fragmentation is low: Only the Br- and [M-Br]- ions are detected, and [M-H]- is observed only in the case of 4-Br-biphenyl and parent anion lifetimes as long as 165 µs are observed. Such lifetimes are contradictory to the dissociation rates of 2- and 4-bromobiphenyl, as measured by the pulse radiolysis method to be 3.2 × 1010 and >5 × 1010 s-1, respectively. The discrepancy is plausibly explained by our calculation of the potential energy surface of the dissociating anion. Isolated in vacuum, the bromide anion can orbit the polarized aromatic radical at a long distance. A series of local minima on the potential energy surface allows for a roaming mechanism prolonging the detection time of such weakly bound complex anions. The present results illuminate the behavior recently observed in a series of bromo-substituted compounds of biological as well as technological relevance.

[Psychophysiological nature of the "aircraft perception"]. / O psikhofiziologicheskoi prirode "chuvstva samoleta".

On the basis of reported data and questionnaires filled in by 26 pilots and 60 cadets an attempt was made to give a psychophysiological characterization to the "aircraft perception". It was compared with the characteristics of motor skills and thus the "aircraft perception" was interpreted as an objective property of flying skills, i.e. a specific expression of automatic actions the pilot performs when flying a plane. At a certain stage of the development of the flying skills some movements are controlled via direct sensations and perceptions of noninstrumented signals. The "aircraft sensation" unloads the pilot's attention allowing him to concentrate on other problems.