Paul Neill

Lifetime of the bound excited level in Ni

The intrinsic lifetime of the upper level in the bound-bound 3d(9) 4s(2) D-2(3/2) -> 3d(9) 4s(2) D-2(5/2) radiative transition in Ni- was measured to be 15.1 +/- 0.4 s. The experiment was performed at cryogenic temperatures in one of the ion-beam storage rings of the Double ElectroStatic Ion Ring ExpEriment facility at Stockholm University. The storage lifetime of the Ni- ion beam was measured to be close to 5 min at a ring temperature of 13 K.

Spatially resolved single crystal x-ray spectropolarimetry of wire array z-pinch plasmas

A recently developed single-crystal x-ray spectropolarimeter has been used to record paired sets of polarization-dependent and axially resolved x-ray spectra emitted by wire array z-pinches. In this measurement, two internal planes inside a suitable crystal diffract the x-rays into two perpendicular directions that are normal to each other, thereby separating incident x-rays into their linearly polarized components. This paper gives considerations for fielding the instrument on extended sources. Results from extended sources are difficult to interpret because generally the incident x-rays are not separated properly by the crystal. This difficulty is mitigated by using a series of collimating slits to select incident x-rays that propagate in a plane of symmetry between the polarization-splitting planes. The resulting instrument and some of the spatially resolved polarized x-ray spectra recorded for a 1-MA aluminum wire array z-pinch at the Nevada Terawatt Facility at the University of Nevada, Reno will be presented.

Measuring the 2D3/2 Ni- excited state lifetime in DESIREE

Experimental studies of the radiative lifetime of the sole excited state in the nickel anion are presented. Beams of Ni- stored in DESIREE at cryogenic temperatures were subject to photodetachment at different photon energies and the resulting neutrals collected. Preliminary analysis of the decay in neutral production yields a radiative lifetime of approximately 15 seconds for the 3d94s2 2D3/2 excited state.

Lifetime of the 1s2p 1P1 excited level in Fe24

Measurements of the spectrum of Fe24+ in the 1.845 A to 1.885 A range obtained on the EBIT‐I electron beam ion trap at Lawrence Livermore National Laboratory were used for determining the radiative lifetime of the 1s2p 1P1 excited state. The spectrum contains electric dipole forbidden transitions at 1.855A (“x”) and 1.868A (“z”) whose lineshape is well represented by a Gaussian line profile and is assumed to be due primarily to Doppler and instrumental broadening. The Gaussian contribution is assumed to be the same for all lines in the spectrum. This assumption simplifies the problem when considering a more complex combination of broadening mechanisms. For allowed transitions such as 1s2p 1P1 → 1s2 1S0, “w”, at 1.850 A we assume a Voigt profile. In the simplest case this combines both natural (Lorentzian) and Doppler (Gaussian) broadening effects which contribute to the width of the spectral line. With the Gaussian contribution determined from lines “x” and “z”, deconvolving the Gaussian from the Voigt pr...