International audienceVarious manganese valence quantification methods using manganese L2,3 and oxygen K electron energy loss near-edge spectra (ELNES) were applied to determine the relative portions of individual valence state in a mixed (Mn3+, Mn4+) valence system. Multiple linear least-squares (MLLS) fitting of Mn L2,3 ELNES using reference spectra and Gaussian peak fitting of Mn L3 edge are newly developed and the feasibility of these methods was tested on a set of cryptomelane minerals with different valence states. The selection of appropriate standards is crucial to the success of the MLLS method. The O K-edge structures for manganese oxides can provide valuable guidance in the selection of appropriate reference spectra for quantitative determination of Mn valence state. Gaussian peak fitting, however, failed to determine the Mn valence for (Mn3+, Mn4+) minerals due to the small separation between the primary L3 peaks from Mn4+ and Mn3+ valence. As to the methods based on calibration curves, the energy difference between Mn L3 and oxygen K, i.e., ΔE (L3-O K) vs. valence, is the most valence-sensitive method in the range of Mn3+ and Mn4+ and yields good agreement with the actual values

Transmission electron microscope (TEM) imaging techniques combined with focused ion beam sample preparation were used to calibrate the solar energetic particle track production rate in lunar samples. Track density measurements by TEM as a function of depth were obtained from lunar rock 64455 that has a well‐constrained exposure age of 2 Myr giving a track production rate of 4.4 ± 0.4 × 104 tracks cm−2 yr−1 for a 2π exposure at 1 AU. The typical space weathering effects in mature lunar soils (both vapor‐deposited rims and solar wind‐damaged rims) accumulate in ˜106 yr based on the new calibration applied to track densities in individual grains. Solar wind‐damaged rim widths in anorthite and olivine follow a power law relationship with track density and achieve steady‐state widths in a few Myr. Vapor‐deposited rim widths show no correlation with exposure age suggesting that their formation is episodic with the full width of vapor‐deposited rims accumulating in a single or a few rare impact events. Solar wind‐damaged rim development was modeled using the stopping range of ions in matter code. Modeling shows that the solar wind‐damaged rims develop rapidly and approach steady‐state values in 105–106 yr. Anorthite and olivine record similar track densities for similar exposure ages, but their structural response to solar wind irradiation differs significantly. Solar wind‐damaged rims on olivine are not amorphous in contrast to modeling and high flux laboratory experiments and a model is proposed to account for their different response to solar wind irradiation.

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