New insights on Br speciation in volcanic glasses and structural controls on halogen degassing

Abstract The volcanic degassing of halogens, and especially of the heavier Br and I, received increased attention over the last 20 years due to their significant effect on atmospheric chemistry, notably the depletion of stratospheric ozone. While the effect of melt composition on halogen diffusion, solubility, or fluid-melt partitioning in crustal magma chambers has been thoroughly studied, structural controls on halogen incorporation in silicate melts remain poorly known, with only few studies available in simplified borosilicate or haplogranite compositions. Here, we demonstrate that high-energy resolution fluorescence detection X-ray absorption spectroscopy (HERFD-XAS) with a crystal analyzer spectrometer (CAS) is well-suited for the study of Br speciation in natural volcanic glasses which can contain lower Br concentrations than their laboratory analogs. Especially, HERFD-XAS results in sharper and better-resolved XANES and EXAFS features than previously reported and enables detection limits for EXAFS analysis down to 100 ppm when previous studies required Br concentrations above the 1000 ppm level. XANES and EXAFS analyses suggest important structural differences between synthetic haplogranitic glass, where Br is surrounded by Na and next-nearest oxygen neighbors, and natural volcanic glasses of basaltic to rhyodacitic compositions, where Br is incorporated in at least three distinct sites, surrounded by Na, K, or Ca. Similar environments, involving both alkali and alkaline earth metals have already been reported for Cl in Ca-bearing aluminosilicate glass and our study thus underlines that the association of Br with divalent cations (Ca2+) has been underestimated in the past due to the use of simplified laboratory analogs. Overall, similarities in Cl and Br structural environments over a large array of compositions (46–67 wt% SiO2) suggest that melt composition alone may not have a significant effect on halogen degassing and further support the coupled degassing of Cl and Br in volcanic systems.

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High energy resolution spectrometer for the dedicated STEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100112725 ◽

1984 ◽

Vol 42 ◽

pp. 558-559 ◽

Cited By ~ 1

Author(s):

P.E. Batson

Keyword(s):

Collection Efficiency ◽

Core Loss ◽

Beam Current ◽

High Energy ◽

High Energy Resolution ◽

Acquisition Time ◽

Good Definition ◽

Loss Analysis ◽

Definition Of ◽

Acceleration Voltage

Use of the STEM to obtain precise electronic information has been hampered by the lack of energy loss analysis capable of a resolution and accuracy comparable to the 0.3eV energy width of the Field Emission Source. Recent work by Park, et. al. and earlier by Crewe, et. al. have promised magnetic sector devices that are capable of about 0.75eV resolution at collection angles (about 15mR) which are great enough to allow efficient use of the STEM probe current. These devices are also capable of 0.3eV resolution at smaller collection angles (4-5mR). The problem that arises, however, lies in the fact that, even with the collection efficiency approaching 1.0, several minutes of collection time are necessary for a good definition of a typical core loss or electronic transition. This is a result of the relatively small total beam current (1-10nA) that is available in the dedicated STEM. During this acquisition time, the STEM acceleration voltage may fluctuate by as much as 0.5-1.0V.

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Polar Middle Atmospheric Responses to Medium Energy Electron (MEE) Precipitation Using Numerical Model Simulations

Atmosphere ◽

10.3390/atmos12020133 ◽

2021 ◽

Vol 12 (2) ◽

pp. 133

Author(s):

Ji-Hee Lee ◽

Geonhwa Jee ◽

Young-Sil Kwak ◽

Heejin Hwang ◽

Annika Seppälä ◽

...

Keyword(s):

Climate Model ◽

Middle Atmosphere ◽

Meridional Circulation ◽

Stratospheric Ozone ◽

High Energy ◽

Chemical Changes ◽

Temperature Changes ◽

Mesospheric Temperature ◽

High Energy Electrons ◽

Circulation Changes

Energetic particle precipitation (EPP) is known to be an important source of chemical changes in the polar middle atmosphere in winter. Recent modeling studies further suggest that chemical changes induced by EPP can also cause dynamic changes in the middle atmosphere. In this study, we investigated the atmospheric responses to the precipitation of medium-to-high energy electrons (MEEs) over the period 2005–2013 using the Specific Dynamics Whole Atmosphere Community Climate Model (SD-WACCM). Our results show that the MEE precipitation significantly increases the amounts of NOx and HOx, resulting in mesospheric and stratospheric ozone losses by up to 60% and 25% respectively during polar winter. The MEE-induced ozone loss generally increases the temperature in the lower mesosphere but decreases the temperature in the upper mesosphere with large year-to-year variability, not only by radiative effects but also by adiabatic effects. The adiabatic effects by meridional circulation changes may be dominant for the mesospheric temperature changes. In particular, the meridional circulation changes occasionally act in opposite ways to vary the temperature in terms of height variations, especially at around the solar minimum period with low geomagnetic activity, which cancels out the temperature changes to make the average small in the polar mesosphere for the 9-year period.

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Spin-resolved and high-energy-resolution XPS studies of the 3sand 2slevels of metallic cobalt

Physical Review B ◽

10.1103/physrevb.49.2040 ◽

1994 ◽

Vol 49 (3) ◽

pp. 2040-2046 ◽

Cited By ~ 32

Author(s):

D. G. Van Campen ◽

L. E. Klebanoff

Keyword(s):

Energy Resolution ◽

High Energy ◽

High Energy Resolution ◽

Metallic Cobalt

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First results of SRC’s new high‐energy resolution variable line density grating monochromator beamline: HERMON

Review of Scientific Instruments ◽

10.1063/1.1145731 ◽

1995 ◽

Vol 66 (2) ◽

pp. 2072-2074 ◽

Cited By ~ 13

Author(s):

M. Bissen ◽

M. Fisher ◽

G. Rogers ◽

D. Eisert ◽

K. Kleman ◽

...

Keyword(s):

Energy Resolution ◽

High Energy ◽

High Energy Resolution ◽

Line Density ◽

Variable Line ◽

First Results ◽

Grating Monochromator

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High-Energy-Resolution Fluorescence-Detected X-ray Absorption of the Q Intermediate of Soluble Methane Monooxygenase

Journal of the American Chemical Society ◽

10.1021/jacs.7b09560 ◽

2017 ◽

Vol 139 (49) ◽

pp. 18024-18033 ◽

Cited By ~ 50

Author(s):

Rebeca G. Castillo ◽

Rahul Banerjee ◽

Caleb J. Allpress ◽

Gregory T. Rohde ◽

Eckhard Bill ◽

...

Keyword(s):

Energy Resolution ◽

Methane Monooxygenase ◽

High Energy ◽

High Energy Resolution ◽

X Ray ◽

Soluble Methane Monooxygenase ◽

X Ray Absorption

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In-situ observation of trapped carriers in organic metal halide perovskite films with ultra-fast temporal and ultra-high energetic resolutions

Nature Communications ◽

10.1038/s41467-021-21946-2 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Kanishka Kobbekaduwa ◽

Shreetu Shrestha ◽

Pan Adhikari ◽

Exian Liu ◽

Lawrence Coleman ◽

...

Keyword(s):

Cross Sections ◽

High Energy ◽

High Energy Resolution ◽

In Situ Observation ◽

Trap States ◽

Tunneling Mechanism ◽

Photocurrent Spectroscopy ◽

Metal Halide Perovskite ◽

Halide Perovskite

AbstractWe in-situ observe the ultrafast dynamics of trapped carriers in organic methyl ammonium lead halide perovskite thin films by ultrafast photocurrent spectroscopy with a sub-25 picosecond time resolution. Upon ultrafast laser excitation, trapped carriers follow a phonon assisted tunneling mechanism and a hopping transport mechanism along ultra-shallow to shallow trap states ranging from 1.72–11.51 millielectronvolts and is demonstrated by time-dependent and independent activation energies. Using temperature as an energetic ruler, we map trap states with ultra-high energy resolution down to < 0.01 millielectronvolt. In addition to carrier mobility of ~4 cm2V−1s−1 and lifetime of ~1 nanosecond, we validate the above transport mechanisms by highlighting trap state dynamics, including trapping rates, de-trapping rates and trap properties, such as trap density, trap levels, and capture-cross sections. In this work we establish a foundation for trap dynamics in high defect-tolerant perovskites with ultra-fast temporal and ultra-high energetic resolution.

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AN EMPIRICAL MODEL OF PRODUCTION AND ATTENUATION OF FLUORESCENCE LIGHT IN ATMOSPHERE FOR SATELLITE-BASED ULTRA HIGH ENERGY COSMIC RAY EXPERIMENTS

International Journal of Modern Physics D ◽

10.1142/s0218271811018822 ◽

2011 ◽

Vol 20 (03) ◽

pp. 299-317

Author(s):

E. STRAZZERI ◽

O. CATALANO ◽

B. SBARUFATTI

Keyword(s):

Stratospheric Ozone ◽

Cosmic Ray ◽

High Energy ◽

Fluorescence Yield ◽

Ultra High Energy ◽

Atmospheric Conditions ◽

Atmospheric Transmission ◽

Emission Point ◽

Geographical Variations ◽

Fluorescence Light

In the context of detection of Ultra High Energy Cosmic Ray (UHECR) showers from space the details of fluorescence light production and transmission in the atmosphere are given. An analytical model of the fluorescence yield, in dependence on nitrogen molecular parameters and the atmospheric conditions, is presented. Seasonal and geographical variations of the total fluorescence photon yield between 300 nm and 400 nm in air excited by 0.85 MeV electrons are shown as a function of the altitude, using different atmospheric models. In the frame of a satellite-based UHECR experiment the fluorescence yield has been corrected by the overall atmospheric transmission which takes into account, in the simplest approximation, the wavelength-dependent scattering and absorption of the fluorescence light from air molecules, from stratospheric ozone, and from aerosol. The effect of the atmospheric attenuation on the fluorescence yield is shown as a function of the altitude of the emission point of light.

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