skip to main content

Title: Ionization induced plasma grating and its applications in strong-field ionization measurements
; ; ; ; ; ;
Award ID(s):
Publication Date:
Journal Name:
Plasma Physics and Controlled Fusion
Sponsoring Org:
National Science Foundation
More Like this
  1. The definition of ambient ionization is updated from “no sample preparation” to sample preparation proximal and in real time with the ionization and analysis step. We differentiate between ambient ionization methods and the direct and hyphenated techniques. Ambient ionization has been reviewed many times and we summarise some of the approaches that reviews have taken to categorize the many ambient ionization methods. Due to the large number of permutations, frequent redundancy and complexity of the 80+ techniques developed so far, none of the review classifications is successful in classifying all the ambient ionization methods based on the chosen scheme. Likewise our classification based on major sample preparation method also fails at finding a good category for every method, but it does highlight the central role that real-time, proximal sample preparation plays in ambient analysis.
  2. Abstract Stellar population models produce radiation fields that ionize oxygen up to O +2 , defining the limit of standard H ii region models (<54.9 eV). Yet, some extreme emission-line galaxies, or EELGs, have surprisingly strong emission originating from much higher ionization potentials. We present UV HST/COS and optical LBT/MODS spectra of two nearby EELGs that have very high-ionization emission lines (e.g., He ii λλ 1640,4686 C iv λλ 1548,1550, [Fe v ] λ 4227, [Ar iv ] λλ 4711,4740). We define a four-zone ionization model that is augmented by a very high-ionization zone, as characterized by He +2 (>54.4 eV). The four-zone model has little to no effect on the measured total nebular abundances, but does change the interpretation of other EELG properties: we measure steeper central ionization gradients; higher volume-averaged ionization parameters; and higher central T e , n e , and log U values. Traditional three-zone estimates of the ionization parameter can underestimate the average log U by up to 0.5 dex. Additionally, we find a model-independent dichotomy in the abundance patterns, where the α /H abundances are consistent but N/H, C/H, and Fe/H are relatively deficient, suggesting these EELGs are α /Fe-enriched by more than threemore »times. However, there still is a high-energy ionizing photon production problem (HEIP 3 ). Even for such α /Fe enrichment and very high log U s, photoionization models cannot reproduce the very high-ionization emission lines observed in EELGs.« less