Angular momentum of gaussian light beams

Analysis of the orbital angular momentum of paraxial light beams shows that a key role in the formation of this quantity is played by phase relations between longitudinal and transverse radiation fields. When a light beam is circularly polarized or has a helical wave front, the azimuthal component of the Poynting vector and the density of orbital angular momentum prove to be non-zero. In the case of circularly polarized radiation, the azimuthal component of the Poynting vector and the density of the orbital angular momentum can change the sign at different points in the cross section of the light beam, while the total orbital momentum of the beam remains quantized.     

Synthesis of (+)-disparlure from diethyl (−)-malate via opening and fragmentation of the three-membered ring in tertiary cyclopropanols

(+)-Disparlure [(7R,8S)-7,8-epoxy-2-methyloctadecane, pheromone of the gypsy moth Lymantria dispar L.] was synthesized starting from diethyl (?)-malate via cyclopropanation of the ester groups, selective protection of the 1,3-diol functionality, and successive opening and fragmentation of the three-membered rings in the corresponding tertiary cyclopropanols as key stages.