Photodehydrocyclizations of stilbene-like compounds VIII: Synthesis of hexaheliceno[3,4-c]hexahelicene
The synthesis of a new double helicene, hexaheliceno[3,4-c]hexahelicene, has been described. Of two possible diastereomers only one has been obtained. Presumably the product has the racemic configuration but this assignment is not yet definite.
Double helicenes: Diphenanthro[4,3-a; 3′,4′-o]picene and benzo[s]diphenanthro[4,3-a; 3′,4′-o]picene
Abstract The synthesis and NMR spectra of the title compounds are described. An X-ray diffraction study, carried out by Dr. J. D. Dunitz (ETH, Zurich), showed that the only product isolated from the photocyclisation of 6 has the dl configuration.
Magnetic plasma confinement for laser ion source.
A laser ion source (LIS) can easily provide a high current beam. However, it has been difficult to obtain a longer beam pulse while keeping a high current. On occasion, longer beam pulses are required by certain applications. For example, more than 10 micros of beam pulse is required for injecting highly charged beams to a large sized synchrotron. To extend beam pulse width, a solenoid field was applied at the drift space of the LIS at Brookhaven National Laboratory. The solenoid field suppressed the diverging angle of the expanding plasma and the beam pulse was widened. Also, it was observed that the plasma state was conserved after passing through a few hundred gauss of the 480 mm length solenoid field.