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Aims.Interstellar ice chemistry is a fundamental driver of the molecular complexity observed within the interstellar medium. Moreover, the chemical evolution of icy mantles is predominantly influenced by the energetic processes to which they are exposed. Differences between radiolytic and photolytic pathways for the formation of complex organic molecules (COMs) can lead to significant variations in the resulting molecular abundances. Methods.Application of Chirped Pulse ICE enables the energetic processing of astrophysical ices through both vacuum ultraviolet photolysis and high-energy electron bombardment, facilitating direct comparison of the chemical outcomes produced by each radiation source. Within a single apparatus, ices are characterized in the condensed phase using reflection-absorption infrared spectroscopy, and in the gas phase directly following temperature-programmed desorption via chirped-pulse millimeter-wave rotational spectroscopy coupled with buffer gas cooling. Comparative energetic processing of two parent ices, methyl and ethyl cyanide (CH₃CN and CH₃CH₂CN), reveals several key findings. Results.Following radiolysis, the formation of ketenimine (CH₂CNH) from methyl cyanide increases by a factor of 3.9–5.9 relative to hydrogen cyanide (HCN) production, compared to photolysis, with detection limited to the condensed phase. This enhancement increases to 7.0–8.3 for methyl ketenimine (CH₃CHCNH) formation from ethyl cyanide. In contrast, the abundance of the corresponding isonitrile relative to HCN remains consistent across both radiation sources, as evidenced by its detection in both the condensed and gas phase. Our results suggest that observed imine-to-HCN ratios may be diagnostic tracers of the prevailing energetic processing and chemical pathways to COM formation in specific interstellar environments. 

Chirality in magnetic systems gives rise to a wide range of exotic phenomena, yet its influence in S = 1 chains remains largely unexplored. Here, we present a comprehensive experimental study of a chiral antiferromagnetic (AFM) S = 1 chain, [Ni(pym)(H2O)4]SO4· H2O (pym = pyrimidine), where the Ni(II) octahedral orientation exhibits a four-fold chiral periodicity. Muon spin rotation measurements indicate the onset of long-range magnetic order below TN = 1.82(2) K. Neutron diffraction measurements reveal a chiral AFM order driven by a chiral modulation of the easy-axis anisotropy direction, rather than the typical scenario of Dzyaloshinskii-Moriya interactions, geometrical frustration or higher-order interactions. Inelastic neutron scattering (INS) measurements reveal dispersive spin-wave excitations well described by linear spin-wave theory, with Hamiltonian parameters J0 = 6.81(1)K (intrachain exchange), J′ 1a = −0.091(1)K (interchain exchange), and D = −3.02(1)K (easy-axis single-ion anisotropy). These parameters are further validated by Monte Carlo simulations of the magnetisation. Additionally, the INS data reveal multiple dispersionless bands, suggesting the presence of further excitations beyond the scope of linear spin-wave theory. 

Greenland stadials and interstadials (GS/GI) were millennial climate oscillations during the last glacial period that were originally identified in Greenland ice cores but that have been correlated with environmental change around much of the globe, including in monsoon regimes, with enhanced monsoon rainfall coincident with North Atlantic warming. Hydroclimate variability associated with GS/GI have been investigated in detail using terrestrial (primarily oxygen isotopes in stalagmites) and marine records, particularly for the Southeast Asian monsoon. However, a considerably smaller number of terrestrial records preserve these events in the Indian summer monsoon (ISM), the primary water source for ~2 billion people across South Asia. Here we present the first glacial-age speleothem stable isotope time series from Nepal, located in the ISM regime. UK-1 is a 187 mm tall aragonite stalagmite from the Pokhara Valley of central Nepal, ~150 km west of Kathmandu. The chronology of UK-1, which was established by 8 U/Th dates, all of which fall in stratigraphic order (within the errors), reveals continuous growth from 34,350-31,500 yr BP (Marine Isotope Stage 3); age uncertainties average ±84 yr. Stable isotope samples were measured every 1 mm, corresponding to a temporal resolution of 18 yr. Oxygen isotope ratios range from -5.6‰ to -7.6‰, and share the same timing and structure as Greenland (inter)stadials GS/GI 6 and 5.2 in the NGRIP record. We interpret this as reflecting an amount effect response to a strengthened ISM driven by more (less) poleward migration of the intertropical convergence zone during periods of northern hemisphere warming (cooling). This clear millennial signal in UK-1 is a somewhat unexpected result given that amount effects in oxygen isotopes in precipitation are weak (R^2=0.1) in this area today. UK-1 carbon isotope ratios range from -3‰ to -6‰ (excluding a small number of negative spikes) and exhibit variability coarsely similar to the NGRIP record, with lower (higher) values generally corresponding to GI (GS), possibly due to prior calcite precipitation in voids above the cave concomitant with changes in precipitation. Some periods of antiphasing between carbon and oxygen are also apparent and may reflect flushing of soil carbon dioxide during particularly wet phases. 

Materials composed of spin-1 antiferromagnetic (AFM) chains are known to adopt complex ground states that are sensitive to the single-ion-anisotropy (SIA) energy ( $D$), and intrachain ( $J_0$) and interchain ( $J_{1,2}^{\prime }$) exchange energy scales. While theoretical and experimental studies have extended this model to include various other energy scales, the effect of the lack of a common SIA axis is not well explored. Here we investigate the magnetic properties of $\mathrm{Ni}\left(\mathrm{pyrimidine}\right){\left({\mathrm{H}}_2\mathrm{O}\right)}_2{\left({\mathrm{NO}}_3\right)}_2$, a chain compound where the tilting of Ni octahedra leads to a twofold alternation of the easy-axis directions along the chain. Muon-spin relaxation measurements indicate a transition to long-range order at $T_{\text{N}}=2.3\mathrm{K}$and the magnetic structure is initially determined to be antiferromagnetic and collinear using elastic neutron diffraction experiments. Inelastic neutron scattering measurements were used to find $J_0=5.107\left(7\right)\mathrm{K}, D=2.79\left(1\right)\mathrm{K},J_1^{\prime }=0.00\left(5\right)\mathrm{K}, J_2^{\prime }=0.18\left(3\right)\mathrm{K}$, and a rhombic anisotropy energy $E=0.19\left(9\right)\mathrm{K}$. Mean-field modeling reveals that the ground state structure hosts spin canting of $\varphi \approx 6.5^{\circ }$, which is not detectable above the noise floor of the elastic neutron diffraction data. Monte Carlo simulation of the powder-averaged magnetization, $M\left(H\right)$, is then used to confirm these Hamiltonian parameters, while single-crystal $M\left(H\right)$simulations provide insight into features observed in the data. Published by the American Physical Society2025 

We investigate the magnetic properties of $S=1$antiferromagnetic diamond-lattice, $\mathrm{Ni}{X}_2{\left(\mathrm{pyrimidine}\right)}_2$ $(X=\mathrm{Cl}, \mathrm{Br})$, hosting a single-ion anisotropy (SIA) orientation which alternates between neighboring sites. Through neutron diffraction measurements of the $X=\mathrm{Cl}$compound, the ordered state spins are found to align collinearly along a pseudo-easy axis, a unique direction created by the intersection of two easy planes. Similarities in the magnetization, exhibiting spin-flop transitions, and the magnetic susceptibility in the two compounds imply that the same magnetic structure and a pseudo-easy axis is also present for $X=\mathrm{Br}$. We estimate the Hamiltonian parameters by combining analytical calculations and Monte Carlo (MC) simulations of the spin-flop and saturation field. The MC simulations also reveal that the spin-flop transition occurs when the applied field is parallel to the pseudo-easy axis. Contrary to conventional easy-axis systems, there exist field directions perpendicular to the pseudo-easy axis for which the magnetic saturation is approached asymptotically and no symmetry-breaking phase transition is observed at finite fields. Published by the American Physical Society2024