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Abstract The young and well-studied planetary nebula (PN) NGC 7027 harbors significant molecular gas that is irradiated by luminous, pointlike UV (central star) and diffuse (shocked nebular) X-ray emission. This nebula represents an excellent subject to investigate the molecular chemistry and physical conditions within photon- and X-ray-dominated regions (PDRs and XDRs). As yet, the exact formation routes of CO+and HCO+in PN environments remain uncertain. Here we present ∼2″ resolution maps of NGC 7027 in the irradiation tracers CO+and HCO+obtained with the IRAM NOEMA interferometer, along with SMA CO and HST 2.12μm H2data for context. The CO+map constitutes the first interferometric map of this molecular ion in any PN. Comparison of CO+and HCO+maps reveals strikingly different emission morphologies, as well as a systematic spatial displacement between the two molecules; the regions of brightest HCO+, found along the central waist of the nebula, are radially offset by ∼1″ (∼900 au) outside the corresponding CO+emission peaks. The CO+emission furthermore precisely traces the inner boundaries of the nebula’s PDR (as delineated by near-IR H2emission), suggesting that central star UV emission drives CO+formation. The displacement of HCO+radially outward with respect to CO+is indicative that dust-penetrating soft X-rays are responsible for enhancing the HCO+abundance in the surrounding molecular envelope, forming an XDR. These interferometric CO+and HCO+observations of NGC 7027 thus clearly establish the spatial distinction between the PDR and XDR formed (respectively) by intense UV and X-ray irradiation of molecular gas.
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This content will become publicly available on May 1, 2026
Extreme bandgap polarization doped AlGaN layers on bulk AlN for pn-diodes with an 8.5 MV cm −1 breakdown field and forward current density exceeding 20 kA cm −2
Abstract In this paper we present a study of distribution polarization doped AlxGa1−xN layers and their use in quasi-vertical configuration pn-diodes which exhibited a high breakdown field of ∼8.5 MV cm−1and a large forward current density (∼23 kA cm−2). We also establish their potential use in UVC light emitters by studying the optical emission from a quantum well inserted at the distribution polarization doped pn-junction interface.
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- Award ID(s):
- 2246582
- PAR ID:
- 10609472
- Publisher / Repository:
- Japanese Journal of Applied Physics
- Date Published:
- Journal Name:
- Japanese Journal of Applied Physics
- Volume:
- 64
- Issue:
- 5
- ISSN:
- 0021-4922
- Page Range / eLocation ID:
- 055507
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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