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1. The Detectability of Coronal Mass Ejections in the Low Corona Using Multislit Extreme-ultraviolet Spectroscopy

   https://doi.org/10.3847/1538-4357/adc10a  

   Chan_陳, Lami 霖誼; Bai, Xianyong; Tian, Hui; Feng, Yufei; Xu, Yu; Török, Tibor; Gao, Yuhang; Samanta, Tanmoy; Sun, Zheng (May 2025, The Astrophysical Journal)

   Abstract The spectra of coronal mass ejections (CMEs) in the low corona play a crucial role in understanding their origins and physical mechanisms and enhancing space weather forecasting. However, capturing these spectra faces significant challenges. This paper introduces a scheme of a multislit spectrometer design with five slits, acquiring the global spectra of the solar corona simultaneously with a focus on the spectra of CMEs in the low corona. The chosen wavelength range of the spectrometer (170–180 Å) includes four extreme ultraviolet emission lines (Fex174.53 Å, Feix171.07 Å, Fex175.26 Å, Fex177.24 Å), which provides information on the plasma velocity, density, and temperature. Utilizing a numerical simulation of the global corona for both the on-disk and the off-limb scenarios, we focus on resolving the ambiguity associated with various Doppler velocity components of CMEs, particularly for a fast CME in the low corona. A new application of our decomposition technique is adopted, enabling the successful identification of multiple discrete CME velocity components. Our findings demonstrate a strong correlation between the synthetic model spectra and the inverted results, indicating the robustness of our decomposition method and its significant potential for global monitoring of the solar corona, including CMEs. 

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2. Integrated Silicon Fourier Transform Spectrometer with Broad Bandwidth and Ultra‐High Resolution

   https://doi.org/10.1002/lpor.202000358  

   Li, Ang; Fainman, Yeshaiahu (March 2021, Laser & Photonics Reviews)

   Abstract An ultra‐high resolution Fourier transform spectrometer (FTS) realized in silicon photonic platform that can operate with broad band, narrow band as well as a combination of broad band and narrow band signals is reported. The ultra‐high resolution of the spectrometer is achieved by exploiting multiple techniques: a Michelson interferometer (MI) structure to increase the optical path delay (OPD), a hybrid waveguide design to reduce insertion loss, an optimized heater and air trenches to achieve higher thermal efficiency. Moreover, to further increase the OPD of the spectrometer to increase its resolution, a novel multiple interferometers approach is employed which combines balanced MI withNstatically imbalanced MIs, thereby increasing the OPD of a single MI by factor ofN+ 1. An FTS spectrometer consisting ofN= 2 such MIs is fabricated and experimentally characterized using unknown broad bandwidth input signal spectra of about 180 nm centered around 1550 nm, a narrow line laser input signal, and a combination of broad and narrow band signals demonstrating spectral resolution of about 0.16 nm. 

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3. Miniature computational spectrometer with a plasmonic nanoparticles-in-cavity microfilter array

   https://doi.org/10.1038/s41467-024-47487-y  

   Zhang, Yangxi; Zhang, Sheng; Wu, Hao; Wang, Jinhui; Lin, Guang; Zhang, A Ping (December 2024, Nature Communications)

   Abstract Optical spectrometers are essential tools for analysing light‒matter interactions, but conventional spectrometers can be complicated and bulky. Recently, efforts have been made to develop miniaturized spectrometers. However, it is challenging to overcome the trade-off between miniaturizing size and retaining performance. Here, we present a complementary metal oxide semiconductor image sensor-based miniature computational spectrometer using a plasmonic nanoparticles-in-cavity microfilter array. Size-controlled silver nanoparticles are directly printed into cavity-length-varying Fabry‒Pérot microcavities, which leverage strong coupling between the localized surface plasmon resonance of the silver nanoparticles and the Fabry‒Pérot microcavity to regulate the transmission spectra and realize large-scale arrayed spectrum-disparate microfilters. Supported by a machine learning-based training process, the miniature computational spectrometer uses artificial intelligence and was demonstrated to measure visible-light spectra at subnanometre resolution. The high scalability of the technological approaches shown here may facilitate the development of high-performance miniature optical spectrometers for extensive applications. 

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4. Field induced fragmentation spectra from reactive stage-tandem differential mobility spectrometry

   https://doi.org/10.1039/d0an00665c  

   Fowler, P. E.; Pilgrim, J. Z.; Lee, G.; Eiceman, G. A. (July 2020, The Analyst)

   A planar tandem differential mobility spectrometer was integrated with a middle reactive stage to fragment ions which were mobility selected in a first analyzer stage using characteristic compensation and separation fields. Fragmentation occurred in air at ambient pressure of 660 Torr (8.8 kPa) with electric fields of 10 to 35 kV cm −1 (E/N of 52 to 180 Td) between two 1 mm wide metal strips, located on each analyzer plate between the first and second mobility stages. Field induced fragmentation (FIF) spectra were produced by characterizing, in a last stage, the mobilities of fragment ions from protonated monomers of 43 oxygen-containing volatile organic compounds from five chemical classes. The extent of fragmentation was proportional to E/N with alcohols, aldehydes, and ethers undergoing multiples steps of fragmentation; acetates fragmented only to a single ion, protonated acetic acid. In contrast, fragmentation of ketones occurred only for methyl i-butyl ketone and 2-hexanone. Fragment ion identities were supported by mass-analysis and known fragmentation routes and suggested that field induced fragmentation at ambient pressure can introduce structural information into FIF spectra, establishing a foundation for chemical identification using mobility methods. 

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5. A UV double pass spectrograph for monitoring stellar activity for the Keck Planet Finder

   https://doi.org/10.1117/12.2628149  

   Baker, Ashley; Gibson, Steven; Grillo, Jason; Ishikawa, Yuzo; Howard, Andrew W.; Halverson, Samuel; Rider, Kodi; Jelinsky, Sharon; Deich, Will; Sirk, Martin; et al (January 2022, Proceedings of the SPIE)

   Evans, Christopher J.; Bryant, Julia J.; Motohara, Kentaro (Ed.)

   We present a compact, double-pass cross-dispersed echelle spectrograph that is tailored specifically to cover the 383 nm to 403 nm spectral range and record R∼16,000 spectra of the stellar chromospheric Ca II H and K lines. This `H and K' spectrometer was developed as a subsystem of the Keck Planet Finder (KPF), which is an extremely precise optical (440 - 870 nm) radial velocity spectrograph for Keck I, scheduled for commissioning Fall 2022, with the science objective of measuring precise masses of exoplanets. The H and K spectrometer will observe simultaneously with KPF to independently track the chromospheric activity of the host stars that KPF observes, which is expected to dominate the KPF measurement floor over long timescales. The H and K Spectrometer is fiber fed from the KPF fiber injection unit with total throughput of 4-7% (top of telescope to CCD) over its operating spectral range. Here we detail the optical design trade offs, mechanical design, and first results from alignment and integration testing. 

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