Narrow Results

An electrostatic beam splitter composed of three charged poles for polar molecules in weak-field-seeking states is proposed. First, the schematic diagram is given. Then we calculate the spatial distribution of the electrical field using the finite element software. We simulate the dynamic process of the loading and splitting polar molecules using the classical Monte Carlo method. We investigate the influences of the longitudinal velocity of the incident molecular beam and the voltages on the performance of our beam splitter. In order to alter the splitting ratio of the molecular beam conveniently, we cut off the two output arms of beam splitter at a certain position. Then we study the influences of the voltages and cutting positions on the splitting ratio. At last, we discuss two methods of keeping the height of guiding center nearly unchanged.

Generation of short wavelengths is obtained using the gas cells having different lengths. A Ti:sapphire laser system at 1kHz or 10Hz repetition rate is used to produce high harmonic generation (HHG). The gas cell producing optimum harmonic spectrum is determined using the 1kHz laser system. The optimum harmonic signal is obtained under the phase-matched condition. The total harmonic yield is increased by adjusting argon gas pressure in the different gas cell lengths (length of the interaction mediums). Harmonics up to the 27th order are obtained. The 1D model is used for the calculation of harmonic yield at different interaction lengths. The high-power laser system at the 10Hz repetition rate is used to generate high-order harmonics. The harmonic orders are extended to the 35th harmonic in argon gas. A harmonic spectrum in H₂ gas is generated using different pump laser power. The power dependence of the harmonic signal from H₂ gas is obtained. The variation of the harmonic spectrum for the different cell parameters is explained as a constructive or destructive buildup of generated harmonics while they propagate through the gas cell.

Ettore Majorana was the brightest Italian theoretical physicist of the XX century (actually, Enrico Fermi regarded him as the brightest in the world of his time, and compared him to Galileo and Newton), even if to some people Majorana is often known mainly for his mysterious disappearance, in 1938, when he was 31. In this paper, we present a panoramic view of the main scientific articles published by him, as well as their significance. We also briefly outline his life, the biographical data being based on letters, documents, testimonies discovered or collected by the author during more than four decades, and contained since 1986 in Recami's book quoted in the text. Finally, extensive information and comments are added with regard to the scientific manuscripts left unpublished by Majorana. Two pictures complete the paper.

Various landmarks in the evolution of Alexander Dalgarno from a gifted mathematician to becoming the acknowledged Father of Molecular Astrophysics are noted. His researches in basic atomic and molecular physics, aeronomy (the study of the upper atmosphere) and astrophysics are highlighted.

The emission from atoms and molecules provide our best probes into astronomical environments. Observations of atomic and molecular lines provide information on the abundance of species, the gas temperature and density. When combined with astrochemical models one may infer ionization rates along with heating and cooling rates. This paper will review a few examples of using atoms and molecules as probes. Most of the examples are selected from work done in collaboration with Alex Dalgarno.