High efficiency laser resonance ionization of plutonium

Three-step resonance photoionization spectra of plutonium have been studied with Ti:Sapphire lasers for the development of efficient laser ionization schemes for ultra-trace analysis of Pu isotopes by resonance ionization mass spectrometry. We observed eighteen intermediate excited states of even parity in the energy range 35568–36701 $${\text {cm}}^{-1}$$ cm - 1 , thirteen of them have not been previously documented, and a larger number of high-lying excited states and autoionizing states of odd-parity between 48238 and 49510 $${\text {cm}}^{-1}$$ cm - 1 . Three-color, three-photon ionization schemes via six intermediate states were evaluated under similar ion source operating conditions. This led to a highly efficient three-step scheme with an overall ionization efficiency of $$51.1 \pm 1.3\%$$ 51.1 ± 1.3 % , which is an order of magnitude improvement over the previously reported ionization efficiency for Pu.

Characterizing Oligomeric Hydroxyl Silicon Oils by MALDI-TOF MS With the Pyridine-Modified Matrix

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF) is a powerful technique for analysis of various polymers, but it is still very difficult to characterize silicone oil due to its poor ionization efficiency. In this work, oligomeric hydroxyl silicone oils were successfully characterized by MALDI-TOF, by using pyridine-modified 2,5-dihydroxylbenzoic acid (DHB) as the matrix. Furthermore, the mixed crystal of DHB and hydroxyl silicone oil was analyzed by scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS), and the analytical results verified that modification with pyridine could remarkably improve the solubility of hydroxyl silicone oil in DHB, leading to the enhancement of its ionization efficiency in MALDI. The analysis of the MS spectra of a series of hydroxyl silicone oils indicated that they tended to be ionized by the attachment with Na+, and the average molecular weight and the degree of polymerization were measured for several oligomeric hydroxyl silicon oils.

Extracting the astrophysics of reionization from the Lyα forest power spectrum: a first forecast

ABSTRACT The impact of cosmic reionization on the Lyα forest power spectrum has recently been shown to be significant even at low redshifts (z ∼ 2). This memory of reionization survives cosmological time-scales because high-entropy mean-density gas is heated to ∼3 × 104 K by reionization, which is inhomogeneous, and subsequent shocks from denser regions. In the near future, the first measurements of the Lyα forest 3D power spectrum will be very likely achieved by upcoming observational efforts such as the Dark Energy Spectroscopic Instrument (DESI). In addition to abundant cosmological information, these observations have the potential to extract the astrophysics of reionization from the Lyα forest. We forecast, for the first time, the accuracy with which the measurements of Lyα forest 3D power spectrum can place constraints on the reionization parameters with DESI. Specifically, we demonstrate that the constraints on the ionization efficiency, ζ, and the threshold mass for haloes that host ionizing sources, mturn, will have the 1σ error at the level of ζ = 25.0 ± 11.6 and $\log _{10} (m_{\rm turn}/{\rm M}_\odot) = 8.7^{+0.36}_{-0.70}$, respectively. The Lyα forest 3D power spectrum will thus provide an independent probe of reionization, probably even earlier in detection with DESI, with a sensitivity only slightly worse than the upcoming 21-cm power spectrum measurement with the Hydrogen Epoch of Reionization Array (HERA), i.e. σDESI/σHERA ≈ 1.5 for ζ and σDESI/σHERA ≈ 2.0 for log10(mturn/M⊙). Nevertheless, the Lyα forest constraint will be improved about three times tighter than the current constraint from reionization observations with high-z galaxy priors, i.e. σDESI/σcurrent ≈ 1/3 for ζ.