Debris discs with multiple absorption features in metallic lines: circumstellar or interstellar origin?

We report the sensing and imaging of explosive related chemical and bio-chemical materials by using terahertz time domain spectroscopy (THz-TDS) at standoff distance. The 0.82 THz absorption peak of RDX is observed at a distance up to 30 m away from the emitter and receiver. Multiple absorption features of RDX, 2,4-DNT and Glutamic Acid are identified by using a large scale 2-D imaging system. These results support the feasibility of using THz-TDS technique in remote sensing and detection of chemical materials.

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Interpretations of multiple absorption features in a gamma-ray burst spectrum

The Astrophysical Journal ◽

10.1086/185342 ◽

1988 ◽

Vol 335 ◽

pp. L71 ◽

Cited By ~ 78

Author(s):

E. E. Fenimore ◽

J. P. Conner ◽

R. I. Epstein ◽

R. W. Klebesadel ◽

J. G. Laros ◽

...

Keyword(s):

Gamma Ray ◽

Gamma Ray Burst ◽

Multiple Absorption ◽

Burst Spectrum ◽

Absorption Features

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Observation of microsecond luminescence while studying two DNA-stabilized silver nanoclusters emitting in the 800-900 nm range.

Physical Chemistry Chemical Physics ◽

10.1039/d1cp01731d ◽

2021 ◽

Author(s):

Vanessa Rück ◽

Cecilia Cerretani ◽

Vlad Andrei Neacsu ◽

Mikkel Liisberg ◽

Tom Vosch

Keyword(s):

Visible Region ◽

Silver Nanoclusters ◽

Multiple Absorption ◽

Absorption Features ◽

Nm Range

We investigated two DNA-stabilized silver nanoclusters (DNA-AgNCs) that show multiple absorption features in the visible region, and emit around 811 nm (DNA811-AgNC) and 841 nm (DNA841-AgNC). Both DNA-AgNCs have large...

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SDSS-IV MaNGA: radial gradients in stellar population properties of early-type and late-type galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab449 ◽

2021 ◽

Vol 502 (4) ◽

pp. 5508-5527

Author(s):

Taniya Parikh ◽

Daniel Thomas ◽

Claudia Maraston ◽

Kyle B Westfall ◽

Brett H Andrews ◽

...

Keyword(s):

Stellar Population ◽

Mass Range ◽

Mass Relation ◽

Individual Element ◽

Late Type ◽

Element Abundances ◽

Entire Mass Range ◽

Strong Gradient ◽

Star Formation Histories ◽

Absorption Features

ABSTRACT We derive ages, metallicities, and individual element abundances of early- and late-type galaxies (ETGs and LTGs) out to 1.5 Re. We study a large sample of 1900 galaxies spanning 8.6–11.3 log M/M⊙ in stellar mass, through key absorption features in stacked spectra from the SDSS-IV/MaNGA survey. We use mock galaxy spectra with extended star formation histories to validate our method for LTGs and use corrections to convert the derived ages into luminosity- and mass-weighted quantities. We find flat age and negative metallicity gradients for ETGs and negative age and negative metallicity gradients for LTGs. Age gradients in LTGs steepen with increasing galaxy mass, from −0.05 ± 0.11 log Gyr/Re for the lowest mass galaxies to −0.82 ± 0.08 log Gyr/Re for the highest mass ones. This strong gradient–mass relation has a slope of −0.70 ± 0.18. Comparing local age and metallicity gradients with the velocity dispersion σ within galaxies against the global relation with σ shows that internal processes regulate metallicity in ETGs but not age, and vice versa for LTGs. We further find that metallicity gradients with respect to local σ show a much stronger dependence on galaxy mass than radial metallicity gradients. Both galaxy types display flat [C/Fe] and [Mg/Fe], and negative [Na/Fe] gradients, whereas only LTGs display gradients in [Ca/Fe] and [Ti/Fe]. ETGs have increasingly steep [Na/Fe] gradients with local σ reaching 6.50 ± 0.78 dex/log km s−1 for the highest masses. [Na/Fe] ratios are correlated with metallicity for both galaxy types across the entire mass range in our sample, providing support for metallicity-dependent supernova yields.

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Ultrafast Electron/Energy Transfer and Intersystem Crossing Mechanisms in BODIPY-Porphyrin Compounds

Processes ◽

10.3390/pr9020312 ◽

2021 ◽

Vol 9 (2) ◽

pp. 312

Author(s):

Yusuf Tutel ◽

Gökhan Sevinç ◽

Betül Küçüköz ◽

Elif Akhuseyin Yildiz ◽

Ahmet Karatay ◽

...

Keyword(s):

Energy Transfer ◽

Fluorescence Spectra ◽

Visible Region ◽

Energy Transfer Mechanism ◽

Free Base ◽

Pump Probe ◽

Harvesting Efficiency ◽

Probe Spectroscopy ◽

Absorption Features ◽

Transfer Mechanisms

Meso-substituted borondipyrromethene (BODIPY)-porphyrin compounds that include free base porphyrin with two different numbers of BODIPY groups (BDP-TTP and 3BDP-TTP) were designed and synthesized to analyze intramolecular energy transfer mechanisms of meso-substituted BODIPY-porphyrin dyads and the effect of the different numbers of BODIPY groups connected to free-base porphyrin on the energy transfer mechanism. Absorption spectra of BODIPY-porphyrin conjugates showed wide absorption features in the visible region, and that is highly valuable to increase light-harvesting efficiency. Fluorescence spectra of the studied compounds proved that BODIPY emission intensity decreased upon the photoexcitation of the BODIPY core, due to the energy transfer from BODIPY unit to porphyrin. In addition, ultrafast pump-probe spectroscopy measurements indicated that the energy transfer of the 3BDP-TTP compound (about 3 ps) is faster than the BDP-TTP compound (about 22 ps). Since the BODIPY core directly binds to the porphyrin unit, rapid energy transfer was seen for both compounds. Thus, the energy transfer rate increased with an increasing number of BODIPY moiety connected to free-base porphyrin.

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Plasmon–Molecule Coupling with Directional Absorption Features: A First-Principles Study

Plasmonics ◽

10.1007/s11468-021-01402-z ◽

2021 ◽

Author(s):

Mufasila Mumthaz Muhammed ◽

Junais Habeeb Mokkath

Keyword(s):

First Principles ◽

First Principles Study ◽

Absorption Features

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Integrative 3D Geological Modeling Derived from SWIR Hyperspectral Imaging Techniques and UAV-Based 3D Model for Carbonate Rocks

Remote Sensing ◽

10.3390/rs13153037 ◽

2021 ◽

Vol 13 (15) ◽

pp. 3037

Author(s):

Huy Hoa Huynh ◽

Jaehung Yu ◽

Lei Wang ◽

Nam Hoon Kim ◽

Bum Han Lee ◽

...

Keyword(s):

3D Model ◽

Imaging Techniques ◽

Iron Hydroxide ◽

Spectral Characteristics ◽

Short Wave ◽

Rock Classification ◽

3D Geological Modeling ◽

Logistic Regression Models ◽

Rock Formations ◽

Absorption Features

This paper demonstrates an integrative 3D model of short-wave infrared (SWIR) hyperspectral mapping and unmanned aerial vehicle (UAV)-based digital elevation model (DEM) for a carbonate rock outcrop including limestone and dolostone in a field condition. The spectral characteristics in the target outcrop showed the limestone well coincided with the reference spectra, while the dolostone did not show clear absorption features compared to the reference spectra, indicating a mixture of clay minerals. The spectral indices based on SWIR hyperspectral images were derived for limestone and dolostone using aluminum hydroxide (AlOH), hydroxide (OH), iron hydroxide (FeOH), magnesium hydroxide (MgOH) and carbonate ion (CO32−) absorption features based on random forest and logistic regression models with an accuracy over 87%. Given that the indices were derived from field data with consideration of commonly occurring geological units, the indices have better applicability for real world cases. The integrative 3D geological model developed by co-registration between hyperspectral map and UAV-based DEM using best matching SIFT descriptor pairs showed the 3D rock formations between limestone and dolostone. Moreover, additional geological information of the outcrop was extracted including thickness, slope, rock classification, strike, and dip.

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