Spectroscopic Observation and Ultrafast Coherent Vibrational Dynamics of the Aqueous Phenylalanine Radical

The phenylalanine radical (Phe•) has been proposed to mediate biological electron transport (ET) and exhibit long-lived electronic coherences following attosecond photoionization. However, the coupling of ultrafast structural reorganization to the...

Probable detection of an eruptive filament from a superflare on a solar-type star

Solar flares are often accompanied by filament/prominence eruptions (~104 K and ~1010−11 cm−3), sometimes leading to coronal mass ejections that directly affect the Earth’s environment1,2. ‘Superflares’ are found on some active solar-type (G-type main-sequence) stars3–5, but the filament eruption–coronal mass ejection association has not been established. Here we show that our optical spectroscopic observation of the young solar-type star EK Draconis reveals evidence for a stellar filament eruption associated with a superflare. This superflare emitted a radiated energy of 2.0 × 1033 erg, and a blueshifted hydrogen absorption component with a high velocity of −510 km s−1 was observed shortly afterwards. The temporal changes in the spectra strongly resemble those of solar filament eruptions. Comparing this eruption with solar filament eruptions in terms of the length scale and velocity strongly suggests that a stellar coronal mass ejection occurred. The erupted filament mass of 1.1 × 1018 g is ten times larger than those of the largest solar coronal mass ejections. The massive filament eruption and an associated coronal mass ejection provide the opportunity to evaluate how they affect the environment of young exoplanets/the young Earth6 and stellar mass/angular momentum evolution7.

In-situ spectroscopic observation of dynamic-coupling oxygen on atomically dispersed iridium electrocatalyst for acidic water oxidation

Uncovering the dynamics of active sites in the working conditions is crucial to realizing increased activity, enhanced stability and reduced cost of oxygen evolution reaction (OER) electrocatalysts in proton exchange membrane electrolytes. Herein, we identify at the atomic level potential-driven dynamic-coupling oxygen on atomically dispersed hetero-nitrogen-configured Ir sites (AD-HN-Ir) in the OER working conditions to successfully provide the atomically dispersed Ir electrocatalyst with ultrahigh electrochemical acidic OER activity. Using in-situ synchrotron radiation infrared and X-ray absorption spectroscopies, we directly observe that one oxygen atom is formed at the Ir active site with an O-hetero-Ir-N4 structure as a more electrophilic active centre in the experiment, which effectively promotes the generation of key *OOH intermediates under working potentials; this process is favourable for the dissociation of H2O over Ir active sites and resistance to over-oxidation and dissolution of the active sites. The optimal AD-HN-Ir electrocatalyst delivers a large mass activity of 2860 A gmetal−1 and a large turnover frequency of 5110 h−1 at a low overpotential of 216 mV (10 mA cm−2), 480–510 times larger than those of the commercial IrO2. More importantly, the AD-HN-Ir electrocatalyst shows no evident deactivation after continuous 100 h OER operation in an acidic medium.

Spectral Evolution of an Eruptive Polar Crown Prominence With IRIS Observations

Prominence eruption is closely related to coronal mass ejections and is an important topic in solar physics. Spectroscopic observation is an effective way to explore the plasma properties, but the spectral observations of eruptive prominences are rare. In this paper we will introduce an eruptive polar crown prominence with spectral observations from the Interface Region Imaging Spectrograph (IRIS), and try to explain some phenomena that are rarely reported in previous works. The eruptive prominence experiences a slow-rise and fast-rise phase, while the line-of-sight motions of the prominence plasma could be divided into three periods: 2 hours before the fast-rise phase, opposite Doppler shifts are found at the two sides of the prominence axis; then, red shifts dominate the prominence gradually; in the fast-rise phase, the prominence gets to be blue-shifted. During the second period, a faint component appears in Mg ii k window with a narrow line width and a large red shift. A faint region is also found in AIA 304Å images along the prominence spine, and the faint region gets darker during the expansion of the spine. We propose that the opposite Doppler shifts in the first period is a feature of the polar crown prominence that we studied. The red shifts in the second period are possibly due to mass drainage during the elevation of the prominence spine, which could accelerate the eruption in return. The blue shifts in the third period are due to that the prominence erupts toward the observer. We suggest that the faint component appears due to the decreasing of the plasma density, and the latter results from the expansion of the prominence spine.

Observability of Exo-Atmospheres in emission using Ariel

<p>Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, is a medium-class space mission part of ESA's Cosmic Vision program, due for launch in 2029. Ariel is the first mission dedicated to the spectroscopic observation of a diverse, statistical sample of about 1000 transiting exoplanets, obtaining spectra in transit, eclipse, or both, to answer questions about their composition, formation and evolution. Ariel has adopted a four-tiered approach in which all targets are observed with different SNRs to optimise the science return from the mission. Ariel has two separate instruments (FGS and AIRS) that will perform simultaneous observations across the 0.5-7.8 micron spectral range, which encompasses both the peak emission of exoplanets and the spectral signatures of key molecules. This will enable Ariel to collect statistical information on the composition and the thermal structure of exo-atmospheres, allowing it to reveal underlying trends in exoplanetary populations. In particular, transit spectroscopy is expected to provide the bulk of information on the chemical composition of exo-atmospheres, while eclipses are necessary to constrain their thermodynamic state. In this framework, I report a preliminary study of Ariel targets observed in emission: at first, I investigate the information content from Tier 1 data, where spectra from the full population of Ariel targets are observed with low SNR, and binned as if Ariel were a multi-band photometer to increase the SNR. I then investigate the effectiveness of Ariel in detecting chemical-physical trends in exoplanetary populations observed in Tier 2, designed to reach SNR in excess of 7 on spectra binned to roughly half the spectral resolution of the focal planes, as specified by the mission requirements.</p>

Operando spectroscopic observation of dynamic-coupling oxygen on single-atomic iridium catalyst for acidic water oxidation

Uncovering the dynamics of active sites under working state is crucial to realizing increased activity, enhanced stability and reduced cost of oxygen evolution reaction (OER) electrocatalysts in proton exchange membrane electrolytes. Herein, we identify at atomic level a potential-driven dynamic-coupling oxygen on the hetero-nitrogen configured single-atomic Ir sites (HN-Ir NC) during OER working conditions to successfully endow the single-atomic Ir catalyst with an ultrahigh electrochemical acidic-OER activity. Using operando synchrotron radiation infrared and X-ray absorption spectroscopies, we directly observe in the experiment that a dynamic oxygen atom is formed at the Ir site with the O-hetero-Ir-N4 structure as more electrophilic active center and then effectively promote the generation of the key *OOH intermediates under working potentials, which is exceptionally favourable for the dissociation of H2O over Ir sites and resistance to over-oxidation and dissolution of the active sites.The optimal single-atomic HN-Ir NC catalyst delivers a large mass activity of 2860 A gmetal−1 and a huge turnover frequency of 5110 h− 1 at a low overpotential of 216 mV (10 mA cm− 2), 480˗510 times than that of commercial IrO2 catalyst. More importantly, the HN-Ir NC catalyst shows no evident deactivation after continuous 100 h OER operation in acidic medium.

Abstract P-10: Solvatochromic Fluorescent Dyes Tested for Spectroscopic Measurements of Protein Conformational Dynamics

Background: Recoverin is a 23 kDa protein, belonging to the superfamily of EF-hand Ca2+-binding proteins. One of the functions of recoverin is to regulate the activity of the rhodopsin kinase GRK1, which regulates the activity of rhodopsin. In dim ambient light, the level of calcium in the rod cells of the retina is high, so recoverin binds to and inhibits rhodopsin kinase, leaving rhodopsin very sensitive to photons to enable the eye to detect visual signals even under low-light conditions. Many biophysical methods have previously been used to study the conformational dynamics of recoverin, including NMR, SPR and fluorescence spectroscopy. Here we describe fluorescent solvatochromic dyes suitable for spectroscopic observation of conformational changes in recoverin. Methods: We tested four fluorescent dyes, which were covalently attached to Cys39 of recoverin via the thiol-maleimide interaction. Results: Two out of four labeled recoverin samples showed EGTA-induced changes in the fluorescence lifetime and excitation and emission spectra. Conclusion: Our experiments show solvatochromic fluorescent dyes that can be successfully used for spectroscopic observation of conformational dynamics in proteins.