Hydrogenic Transitions in Multiply Charged Fe and Ni Ions

Ten lines in the range 3880≦λ≦5666 Å in the beam-foil spectrum of iron have been identified with specific hydrogenic transitions in Fe iv-viii. The same transitions were observed from Ni and Ar beams. Deviations from the hydrogenic wavelengths are shown to be consistent with that expected from core polarization. The absence of these lines in astrophysical sources is discussed. A wavelength table is presented for identification of hydrogenic transitions to be expected in beam-foil spectra

Range of heavy ions in solids

The ranges of N, Ne, Ar, Kr, and Xe ions in Be, B, C, and Al have been measured to ±10% for incident ion energy 50-500 kev. A monoenergetic ion beam from an electrostatic accelerator strikes a thick target of the absorber, and the penetration depth is determined by a momentum analysis of monoenergetic protons elastically scattered from the target and the embedded atoms. An expression relating the penetration depth to the actual path length is derived. A linear range-energy behavior is found for Ar, Kr, and Xe ions; for N and Ne ions dE/dX increases with ion energy. The experimental ranges are 20% shorter than theoretical values based on energy loss by elastic nuclear collisions. By including electronic contributions to the stopping process, good agreement with experiment is achieved

Lifetimes, transition probabilities, and level energies in Fe I

We use time-resolved laser-induced fluorescence to measure the lifetime of 186 Fe levels with energies between 25 900 and 60 758 cm . Measured emission branching fractions for these levels yield transition probabilities for 1174 transitions in the range 225-2666 nm. We find another 640 Fe transition probabilities by interpolating level populations in the inductively coupled plasma spectral source. We demonstrate the reliability of the interpolation method by comparing our transition probabilities with absorption oscillator strengths measured by the Oxford group [Blackwell et al., Mon. Not. R. Astron. Soc. 201, 595-602 (1982)]. We derive precise Fe level energies to support the automated method that is used to identify transitions in our spectra

Lifetimes, branching ratios, and transition probabilities in Co ii

The radiative lifetime of 14 levels in the z^5F, z^5D, and z^5G terms of Co ii have been measured with use of time-resolved laser fluorescence spectroscopy with a Co+-ion beam. Our lifetime values are shorter by 15–50 % than earlier results from beam-foil time-of-flight measurements. The lifetimes were converted to 41 individual transition probabilities with use of branching ratios measured on spectra recorded with the 1-m Fourier-transform spectrometer at the Kitt Peak National Observatory. On average our transition probabilities agree with those of Kurucz and Peytremann; for ΔS=1 transitions their calculated values are lower than our experimental results by a factor of ∼(1/4)

The stopping cross section of gases for protons, 30-600 kev

The stopping cross section of H2, He, O2, air, N2, Ne, A, Kr, Xe, H2O, NH3, NO, N2O, CH4, C2H2, C2H4, and C6H6 for protons has been measured over the energy range Ep=30-600 kev. An electrostatic analyzer measures the energy of protons incident on a gas cell, and the transmitted beam energy is measured with a magnetic spectrometer. The gas cell is closed off with thin aluminum windows. Comparison of the molecular stopping cross section of the compounds with the values obtained by summing the constituent atomic cross sections shows that Bragg's rule does not hold for any of these compounds below Ep=150 kev; for NO the additive rule does not hold at any energy studied. Above 150 kev the stopping cross section of carbon is obtained by subtracting the hydrogen contribution from the values measured for the hydrocarbons. Average ionization potentials are calculated from these measurements. A range energy relation for protons in air is included. Sources of error are discussed; the probable error of the stopping cross section measurements varies between 2-4 percent

Reaction Na23(p,α)Ne20 for proton bombarding energies from 100 to 450 keV

The Na23(p,α)Ne20 reaction has been studied for proton bombarding energies in the range 100 to 450 keV. Four narrow resonances were observed at proton bombarding energies Ep=286, 338, 374, and 445 keV. Excitation functions were taken at each of these resonances, and the alpha yield, width, and resonance energy was determined for each resonance. On the basis of angular distribution measurements, spin and parity assignments have been made for the resonances at Ep=286, 338, and 374 keV. Upper limits have been established for the nonresonant cross-section factor S and for the alpha yield from resonances not observed. The Na23(p, α)Ne20 reaction rate in stars is computed for temperatures (5-10)×10^8 °K, the temperature range in which carbon burning takes place

The stopping cross section of D2O ice

The energy loss of protons and deuterons in D2O ice has been measured over the energy range Ep=18-541 kev using the double focusing magnetic spectrometer to measure the energy of the particles after they have traversed a known thickness of the ice target. One method of measurement is used to determine relative values of the stopping cross section as a function of energy, another method measures the absolute values. The results are in very good agreement with the values calculated from Bethe's semi-empirical formula. Possible sources of error are considered and the accuracy of these measurements is estimated to be ±4 percent

Cross Section and Angular Distribution of the D(d,p)T Reaction

The D(d,p)T reaction cross section has been measured by two methods using D2O ice targets. For Ed from 206 to 516 kev, a double-focusing magnetic spectrometer was used to obtain the momentum spectrum of the protons and tritons, from which the reaction cross section can be determined. For Ed from 35 to 550 kev, the proton yield from a thick target was differentiated to obtain the cross section. Both thin and thick target methods were used to measure the angular distribution over the energy range Ed from 35 to 550 kev. The angular distribution is expressed in terms of a Legendre polynomial expansion. Various sources of experimental error are considered and the probable error of the total cross section is found to be ±5 percent

Precise Determination of the Li7(p,α)He4 and Be9(d,α)Li7 Q-Values

A magnetic spectrograph of the double-focusing 180° sector type has recently been constructed in this laboratory and used to measure the energy release in the Li7(p,α)He4 reaction