Photoinduced intramolecular electron transfer in Fe tetracyano-polypyridyl complexes was investigated with static and time-resolved UV-visible absorption and resonant inelastic X-ray scattering which revealed a competition of two relaxation pathways.

Li-and Mn-rich (LMR) layered cathode materials have demonstrated impressive capacity and specific energy density thanks to their intertwined redox centers including transition metal cations and oxygen anions. Although tremendous efforts have been devoted to the investigation of the electrochemically-driven redox evolution in LMR cathode at ambient temperature, their behavior under a mildly elevated temperature (up to ~100 o C), with or without electrochemical driving force, remains largely unexplored. Here we show a systematic study of the thermallydriven surface-to-bulk redox coupling effect in charged Li 1.2 Ni 0.15 Co 0.1 Mn 0.55 O 2. We observed a charge transfer between the bulk oxygen anions and the surface transition metal cations, suggesting that the thermally-enhanced Li + mobility in the hosting LMR lattice could lead to significant redistribution of Li ions. Our results highlight the non-equilibrium state and dynamic nature of LMR material at deeply delithiated state and its relaxation process in response to a mild temperature perturbation.

The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory. Athena is a versatile observatory designed to address the Hot and Energetic Universe science theme, as selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), X-IFU aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over a hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR (i.e. in the course of its preliminary definition phase, so-called B1), browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters, such as the instrument efficiency, spectral resolution, energy scale knowledge, count rate capability, non X-ray background and target of opportunity efficiency. Finally, we briefly discuss the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, touch on communication and outreach activities, the consortium organisation and the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship

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Micro-X is a sounding rocket-borne instrument that uses a microcalorimeter array to perform high-resolution X-ray spectroscopy. This instrument flew for the first time on July 22 nd , 2018 from the White Sands Missile Range, USA. This flight marks the first successful operation of a Transition-Edge Sensor array and its time division multiplexing read-out system in space. This launch was dedicated to the observation of the supernova remnant Cassiopeia A. A failure in the attitude control system prevented the rocket from pointing and led to no time on target. The on-board calibration source provided X-rays in flight, and it is used to compare detector performance during pre-flight integration, flight, and after the successful post-flight recovery. This calibration data demonstrates the capabilities of the detector in a space environment as well as its potential for future flights. 1 The supernova remnant considered for this mission depends on the time of the year. The primary target (Puppis A) is not visible during the summer, so the secondary target was chosen for the first flight.

The Micro-X sounding rocket flew for the first time on July 22, 2018, becoming the first program to fly Transition-Edge Sensors and multiplexing SQUID readout electronics in space. While a rocket pointing failure led to no time on-target, the success of the flight systems was demonstrated. The successful flight operation of the instrument puts the program in a position to modify the payload for indirect galactic dark matter searches. The payload modifications are motivated by the science requirements of this observation. Micro-X can achieve world-leading sensitivity in the keV regime with a single flight. Dark matter sensitivity projections have been updated to include recent observations and the expected sensitivity of Micro-X to these observed fluxes. If a signal is seen (as seen in the X-ray satellites), Micro-X can differentiate an atomic line from a dark matter signature.

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We use narrow spectral lines from the x-ray spectra of various highly charged ions to measure low-energy tail-like deviations from a Gaussian response function in a microcalorimter x-ray spectrometer with Au absorbers at energies from 650 eV to 3320 eV. We review the literature on low energy tails in other microcalorimter x-ray spectrometers and present a model that explains all the reviewed tail fraction measurements. In this model a low energy tail arises from the combination of electron escape and energy trapping associated with Bi x-ray absorbers.