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The Earth Radiation Budget (ERB), a measure of the difference between incoming solar irradiance and outgoing reflected and emitted radiant energy, is a fundamental property of Earth’s climate system. The Libera satellite mission will measure the ERB’s outgoing components to continue the long-term climate data record established by NASA’s Clouds and the Earth’s Radiant Energy System (CERES) mission. In addition to ensuring data continuity, Libera will introduce a novel split-shortwave spectral channel to quantify the partitioning of the outgoing reflected solar component into visible and near-infrared sub-components. However, converting these split-shortwave radiances into the ERB-relevant irradiances requires the development of split-shortwave Angular Distribution Models (ADMs), which demand extensive angular sampling. Here, we show how Rotating Azimuthal Plane Scan (RAPS) parameters—specifically operational cadence and azimuthal scan rate—affect the observational coverage of a defined scene and angular space. Our results show that for a fixed number of azimuthal rotations, a relatively slow azimuthal scan rate of 0.5° per second, combined with more time spent in the RAPS observational mode, provides a more comprehensive sampling of the desired scene and angular space. We also show that operating the Libera instrument in RAPS mode at a cadence between every fifth day and every other day for the first year of space-based operations will provide sufficient scene and angular sampling for the observations to achieve radiance convergence for the scenes that comprise more than half of the expected Libera observations. Obtaining radiance convergence is necessary for accurate ADMs.

One of the most challenging aspects of X‐ray research is the delivery of liquid sample flows into the soft X‐ray beam. Currently, cylindrical microjets are the most commonly used sample injection systems for soft X‐ray liquid spectroscopy. However, they suffer from several drawbacks, such as complicated geometry due to their curved surface. In this study, we propose a novel 3D‐printed nozzle design by introducing microscopic flat sheet jets that provide micrometre‐thick liquid sheets with high stability, intending to make this technology more widely available to users. Our research is a collaboration between the EuXFEL and MAX IV research facilities. This collaboration aims to develop and refine a 3D‐printed flat sheet nozzle design and a versatile jetting platform that is compatible with multiple endstations and measurement techniques. Our flat sheet jet platform improves the stability of the jet and increases its surface area, enabling more precise scanning and differential measurements in X‐ray absorption, scattering, and imaging applications. Here, we demonstrate the performance of this new arrangement for a flat sheet jet setup with X‐ray photoelectron spectroscopy, photoelectron angular distribution, and soft X‐ray absorption spectroscopy experiments performed at the photoemission endstation of the FlexPES beamline at MAX IV Laboratory in Lund, Sweden. Our work presents recent advancements in 3D‐printed nozzles for liquid jet spectroscopy, made possible by the availability of nozzle development and testing facilities at EuXFEL, Germany. We also demonstrate the performance of one of these custom‐designed nozzles in a new flat jet system under commissioning at MAX IV Laboratory in Lund, Sweden, introducing a new injection method to analyze flat liquid surfaces and opening new possibilities for the spectroscopy community.

Most studies of the impact of vibrational excitation on molecular reactivity have focused on reactions with a late barrier (that is, a transition state resembling the products). For an early barrier reaction, conventional wisdom predicts that a reactant's vibration should not couple efficiently to the reaction coordinate and thus should have little impact on the outcome. We report here an in-depth experimental study of the reactivity effects exerted by reactant C-H stretching excitation in a prototypical early-barrier reaction, F + CHD₃. Rather counterintuitively, we find that the vibration hinders the overall reaction rate, inhibits scission of the excited bond itself (favoring the DF + CHD₂ product channel), and influences the coproduct vibrational distribution despite being conserved in the CHD₂ product. The results highlight substantial gaps in our predictive framework for state-selective polyatomic reactivity.

Angular Distribution Models (ADMs) are essential for converting observed radiances from satellite sensors to the energy-budget–relevant quantity of irradiance. In preparation for the NASA Libera mission, this study presents a data-driven framework to identify optimal groupings of International Geosphere–Biosphere Programme (IGBP) surface types for Libera’s split-shortwave ADMs, in an effort to minimize the uncertainty associated with radiance-to-irradiance conversions while maintaining operational feasibility. Using data from the Clouds and the Earth’s Radiant Energy System (CERES) Flight Model 5 (FM-5), K-means clustering is applied within angular bins to capture viewing-geometry-dependent radiometric behavior. These angular clustering solutions are then assessed via hierarchical consensus clustering to derive consistent surface groups. The analysis suggests seven surface groups (K = 7) optimize the surface clustering space. The resulting classifications are broadly consistent with historical CERES–TRMM ADM surface definitions, preserving radiometrically distinct surfaces such as water bodies and snowy surfaces while highlighting opportunities to consolidate vegetative IGBP surface classes. This study provides an objective and physically grounded basis for defining Libera ADM surface groups, ensuring a robust balance between model accuracy and operational simplicity.

Observing the Earth radiation budget (ERB) from satellites is crucial for monitoring and understanding Earth’s climate. One of the major challenges for ERB observations, particularly for reflected shortwave radiation, is the conversion of the measured radiance to the more energetically relevant quantity of radiative flux, or irradiance. This conversion depends on the solar-viewing geometry and the scene composition associated with each instantaneous observation. We first outline the theoretical basis for algorithms to convert shortwave radiance to irradiance, most commonly known as empirical angular distribution models (ADMs). We then review the progression from early ERB satellite observations that applied relatively simple ADMs, to current ERB satellite observations that apply highly sophisticated ADMs. A notable development is the dramatic increase in the number of scene types, made possible by both the extended observational record and the enhanced scene information now available from collocated imager information. Compared with their predecessors, current shortwave ADMs result in a more consistent average albedo as a function of viewing zenith angle and lead to more accurate instantaneous and mean regional irradiance estimates. One implication of the increased complexity is that the algorithms may not be directly applicable to observations with insufficient accompanying imager information, or for existing or new satellite instruments where detailed scene information is not available. Recent advances that complement and build on the base of current approaches, including machine learning applications and semi-physical calculations, are highlighted.

The biharmonic ( ω , 2 ω ) photoionization of atomic inner-shell electrons opens up new perspectives for studying nonlinear light–atom interactions at intensities in the transition regime from weak to strong-field physics. In particular, the control of the frequency and polarization of biharmonic beams enables one to carve the photoelectron angular distribution and to enhance the resolution of ionization measurements by the (simultaneous) absorption of photons. Apart from its quite obvious polarization dependence, the photoelectron angular distributions are sensitive also to the (relative) intensity, the phase difference and the temporal structure of the incoming beam components, both at resonant and nonresonant frequencies. Here, we describe and analyze several characteristic features of biharmonic ionization in the framework of second-order perturbation theory and (so-called) ionization pathways , as they are readily derived from the interaction of inner-shell electrons with the electric-dipole field of the incident beam. We show how the photoelectron angular distribution and elliptical dichroism can be shaped in rather an unprecedented way by just tuning the properties of the biharmonic field. Since such fields are nowadays accessible from high-harmonic sources or free-electron lasers, these and further investigations might help extract photoionization amplitudes or the phase difference of incoming beams.

The Earth’s radiation budget (ERB) is influenced by the top-of-atmosphere (TOA) shortwave radiation flux. The DSCOVR (Deep Space Climate Observatory), equipped with the Earth Polychromatic Imaging Camera (EPIC), offers a unique vantage point from the Sun-Earth Lagrange point 1 for observing Earth. Converting satellite radiance to flux traditionally requires angular distribution models (ADMs) to account for radiation anisotropy, but no such models exist for DSCOVR/EPIC, and their development is complex. To simplify this process, this study introduces a machine learning approach to analyse DSCOVR/EPIC data for global shortwave flux monitoring. Using CERES (Clouds and the Earth’s Radiant Energy System) data as a reference, neural networks were trained to estimate TOA shortwave flux from DSCOVR/EPIC data. Most of the models were effective, with results that correlated with CERES well, the average validation performance of 36 models is 96%. This research highlights the potential of deep space Earth observation for ERB monitoring and suggests applicability for geostationary satellites and lunar observations.

Field measurements of sea waves have been carried out off the coast of Sakhalin Island using an array of three bottom pressure sensors. The stability of statistical characteristics estimated by independent devices comprised in the array has been analyzed. The probability distribution of wave heights qualitatively corresponds to the Glukhovsky distribution but exhibits a lower probability of high wave occurrence. The spatiotemporal spectra of waves are reconstructed. It is shown that the angular distribution of the spectral density of waves over two days of measurements is well described by the theoretical cosine squared distribution, and its width varies in the range of 50°–90°. The dominant direction of wave propagation is from the northeast. An independent method is proposed for estimating the local water depth by data from the array.

The influence of vibrational excitation on chemical reaction dynamics is well understood in triatomic reactions, but the multiple modes in larger systems complicate efforts toward the validation of a predictive framework. Although recent experiments support selective vibrational enhancements of reactivities, such studies generally do not properly account for the differing amounts of total energy deposited by the excitation of different modes. By precise tuning of translational energies, we measured the relative efficiencies of vibration and translation in promoting the gas-phase reaction of CHD₃ with the Cl atom to form HCl and CD₃. Unexpectedly, we observed that C-H stretch excitation is no more effective than an equivalent amount of translational energy in raising the overall reaction efficiency; CD₃ bend excitation is only slightly more effective. However, vibrational excitation does have a strong impact on product state and angular distributions, with C-H stretch-excited reactants leading to predominantly forward-scattered, vibrationally excited HCl.

In this paper, the kinetic properties of single electron and the spatial radiation in tightly focused linearly polarized intense laser fields with different carrier envelope phase under long and short pulse conditions are investigated. The full-space radiation energy distribution, the full-angle optical spectrum of forward radiation, and the full-angle pulse time spectrum of forward radiation are explored in all directions in three dimensions. The study found that the spatial distribution of high-energy electron radiation is no longer fourfold symmetric in a tightly focused pulse intense laser field, and the energy asymmetry coefficient and maximum energy angle are proposed for the first time to quantify them. In addition, it was found that in laser fields with different pulse durations, the electron radiation optical spectra and the radiation pulse time spectral angular distribution exhibit different characteristics. The manifestation and the degree of change affected by the carrier envelope phase are also different. The intensity and angular range of the electron spectra and pulse time spectra in the long and short pulse laser fields were compared, and the ‘Dark Angle’ phenomenon of the forward radiation optical spectrum, along with the interference superposition of the radiation pulse pair, was found.