Two-nucleon pion absorption in 3,4He

Results are presented for π⁺NN → Np yields in ^3,4He relative to πd → pp from (π, p) measurements at energies between 50 and 295 MeV and estimates are given for total cross sections. These yields are nearly proportional to the number of target NN pairs, which is not true for ⁶Li and heavier nuclei. This is believed to indicate that πNN → Np is sensitive to the NN short-range behavior which is deuteron-like for ^3,4He but not always so for NN pairs in other nuclei.     

The C(α, X)11C cross sections at 1.59 and 4.19 GeV

The absolute cross sections for the production of ¹¹C by 1.59 GeV and 4.19 GeV α-particles incident on natural carbon have been measured to be 46.4 ± 1.3 mb and 42.5 ± 1.1 mb respectively. These results, together with data reported at other energies, indicate that the C(α, X)¹¹C cross section becomes approximately constant at a value of about 43 mb for energies above 3 GeV (750 MeV/n). A similar energy dependence is exhibited by the C(p, X)¹¹C reaction whose cross section has been measured previously over an extensive energy range. The C(α, X)¹¹C cross sections are found to be in good agreement with predictions of a semi-empirical model developed to describe nuclear fragmentation.     

Linearised tuning of a cw spin-flip Raman laser using anti-reflection coated cavities

By reducing the electron concentration of the InSb cavity and anti-reflection coating its ends, the frequency tuning of a cw spin-flip Raman laser has been linearised to ?99% of the spontaneous tuning rate, and the magnitude of mode jumps decreased to ? 30 MHz (0.001 cm^-1).     

Analysis of collisional alignment and orientation studied by scattering of spin-polarized electrons from laser excited atoms

A general framework using density matrices is developed for the analysis of atomic excitation by spin-polarized electrons. This framework is applied to the specific case of the 3S _1/2→3P _3/2 transition in Na, as studied by the time-reversed, superelastic process. The scattering is characterized in terms of physical parameters describing the collisionally excitedp-state, i.e., its angular momentum (L _⊥), linear polarization (P _lin), and alignment angle (γ), with these parameters defined separately for singlet and triplet excitation. An expression for the scattering intensity is derived which is valid for arbitrary electron polarization and atomic state preparation. Specific examples are discussed with a view toward complete determination of the relevant scattering amplitudes and phases. Recent experimental results are reevaluated for comparison with theoretical calculations, and suggestions are made for future experiments.     

Literatur

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