Characteristics of Two Types of Grazing Incidence Spectrometers with Holographic Gratings

Two types of grazing incidence spectrometers have been constructed which are applicable to photographic and photo-electric recordings of emission spectra of plasmas in the extreme ultraviolet. The spectrometer SGX-100 with a 1-m Rowland circle covers the wavelengths of 30 to 1500 Å with both a holographic grating (HG) and a ruled one (RG). In this spectrometer, the incidence angle cc to the gratings is continuously variable from 80°to 86°, where the inverse Vodar mounting is adopted to keep a constant line of sight of the spectrometer against a light source. The small grazing incidence spectrometer GIT-30 with a toroidal holographic grating covers the wave-lengths of 150 to 1600 Å. The wavelength scanning is performed by a simple rotation of the grating under a constant angle 142° between the incident and exit beams. These spectrometers were used to observe spectra of emissions from a hollow cathode lamp and linear Z-pinch and plasma-focus discharges. Characteristics of the spectrometers are discussed on the data observed

Precision measurement of the electric quadrupole moment of 31Al and determination of the effective proton charge in the sd-shell

he electric quadrupole coupling constant of the 31Al ground state is measured to be nu_Q = |eQV_{zz}/h| = 2196(21)kHz using two different beta-NMR (Nuclear Magnetic Resonance) techniques. For the first time, a direct comparison is made between the continuous rf technique and the adiabatic fast passage method. The obtained coupling constants of both methods are in excellent agreement with each other and a precise value for the quadrupole moment of 31Al has been deduced: |Q(31Al)| = 134.0(16) mb. Comparison of this value with large-scale shell-model calculations in the sd and sdpf valence spaces suggests that the 31Al ground state is dominated by normal sd-shell configurations with a possible small contribution of intruder states. The obtained value for |Q(31Al)| and a compilation of measured quadrupole moments of odd-Z even-N isotopes in comparison with shell-model calculations shows that the proton effective charge e_p=1.1 e provides a much better description of the nuclear properties in the sd-shell than the adopted value e_p=1.3 e