Abstract Accurate extreme ultraviolet spectra of open N -shell neodymium (Nd) ions were recorded at the electron beam ion trap facility of the National Institute of Standards and Technology. The measurements were performed for nominal electron beam energies in the range of 0.90 keV to 2.31 keV. The measured spectra were then compared with the spectra simulated by a collisional-radiative model utilizing atomic data produced with a fully relativistic atomic structure code. Consequently, 59 lines from Br-like to Ni-like Nd ions were unambiguously identified, most of which were newly assigned in this study. The wavelengths of 9 known lines from Ni-, Cu- and Zn-like Nd ions were in excellent agreement with previous measurements.
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Dielectronic resonances of LMn and LNn (n 4) series in highly charged M-shell tungsten ions
We present spectroscopic measurements and detailed theoretical analysis of inner-shell LMn and LNn (n 4) dielectronic resonances in highly charged M-shell ions of tungsten. The x-ray emission from W49+ through W64+ was recorded at the electron-beam ion trap (EBIT) facility at the National Institute of Standards and Technology with a high-purity Ge detector for electron-beam energies between 6.8 and 10.8 keV. The measured spectra clearly show the presence of strong resonance features as well as direct excitation spectral lines. The analysis of the recorded spectra with large-scale collisional-radiative modeling of the EBIT plasma allowed us to unambiguously identify numerous dielectronic resonances associated with excitations of the inner-shell 2s1/2, 2p1/2, and 2p3/2 electrons.
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- Award ID(s):
- 1806494
- NSF-PAR ID:
- 10180561
- Date Published:
- Journal Name:
- Physical review
- Volume:
- 101
- ISSN:
- 1050-2947
- Page Range / eLocation ID:
- 032503
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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High-resolution x-ray spectra were recorded at the National Institute of Standards and Technology electron beam ion trap (EBIT) using two Johann-type crystal spectrometers, with their dispersion planes oriented parallel and perpendicular to the beam direction. The linear polarizations of the 1s2−1s2l transitions in He-like argon ions were determined from the measured spectra at electron beam energies of 3.87 and 7.91 keV. The theoretical analysis was performed using detailed collisional-radiative modeling of the non-Maxwellian EBIT plasma with the NOMAD code modified to account for magnetic sublevel atomic kinetics. Effects influencing the polarizations of the observed 1s2−1s2l lines were investigated, including radiative cascades, the 1s2 1S0−1s2s 1S0 two-photon transition, and the charge exchange recombination of H-like argon ions. With these included, the measured polarizations of the resonance (1s2 1S0−1s2p 1P1), intercombination (1s2 1S0−1s2p 3P1), and forbidden lines (1s2 1S0−1s2s 3S1, 1s2 1S0−1s2p 3P2 ) were found to be in good agreement with the calculations.more » « less
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Abstract Inner-shell photoelectron spectroscopy provides an element-specific probe of molecular structure, as core-electron binding energies are sensitive to the chemical environment. Short-wavelength femtosecond light sources, such as Free-Electron Lasers (FELs), even enable time-resolved site-specific investigations of molecular photochemistry. Here, we study the ultraviolet photodissociation of the prototypical chiral molecule 1-iodo-2-methylbutane, probed by extreme-ultraviolet (XUV) pulses from the Free-electron LASer in Hamburg (FLASH) through the ultrafast evolution of the iodine 4d binding energy. Methodologically, we employ electron-ion partial covariance imaging as a technique to isolate otherwise elusive features in a two-dimensional photoelectron spectrum arising from different photofragmentation pathways. The experimental and theoretical results for the time-resolved electron spectra of the 4d 3/2 and 4d 5/2 atomic and molecular levels that are disentangled by this method provide a key step towards studying structural and chemical changes from a specific spectator site.more » « less
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Limited approaches exist for imaging and recording spectra of individual nanostructures in the midinfrared region. Here we use infrared photothermal heterodyne imaging (IR-PHI) to interrogate single, high aspect ratio Au nanowires (NWs). Spectra recorded between 2,800 and 4,000 cm−1for 2.5–3.9-μm-long NWs reveal a series of resonances due to the Fabry–Pérot modes of the NWs. Crucially, IR-PHI images show structure that reflects the spatial distribution of the NW absorption, and allow the resonances to be assigned to the
m = 3 andm = 4 Fabry–Pérot modes. This far-field optical measurement has been used to image the mode structure of plasmon resonances in metal nanostructures, and is made possible by the superresolution capabilities of IR-PHI. The linewidths in the NW spectra range from 35 to 75 meV and, in several cases, are significantly below the limiting values predicted by the bulk Au Drude damping parameter. These linewidths imply long dephasing times, and are attributed to reduction in both radiation damping and resistive heating effects in the NWs. Compared to previous imaging studies of NW Fabry–Pérot modes using electron microscopy or near-field optical scanning techniques, IR-PHI experiments are performed under ambient conditions, enabling detailed studies of how the environment affects mid-IR plasmons.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1103/PhysRevA.101.032503
