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Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) is a powerful technique for elemental compositional analysis and depth profiling of materials. However, it encounters the problem of matrix effects that hinder its application. In this work, we introduce a pioneering ToF-SIMS calibration method tailored for SixGeySnz ternary alloys. SixGe1-x and Ge1-zSnz binary alloys with known compositions are used as calibration reference samples. Through a systematic SIMS quantification study of SiGe and GeSn binary alloys, we unveil a linear correlation between secondary ion intensity ratio and composition ratio for both SiGe and GeSn binary alloys, effectively mitigating the matrix effects. Extracted relative sensitivity factor (RSF) value from SixGe1-x (0.07<0.83) and Ge1-zSnz (0.066<0.183) binary alloys are subsequently applied to those of SixGeySnz (0.011<0.113, 0.863<0.935 and 0.023<0.103) ternary alloys for elemental compositions quantification. These values are cross-checked by Atom Probe Tomography (APT) analysis, an indication of the great accuracy and reliability of as-developed ToF-SIMS calibration process. The proposed method and its reference sample selection strategy in this work provide a low-cost as well as simple-to-follow calibration route for SiGeSn composition analysis, thus driving the development of next-generation multifunctional SiGeSn-related semiconductor devices. 

Carbocations play crucial roles during catalytic reactions by dictating the reaction pathways and genuine mechanisms, but the instability of carbocations prevents thorough observations. The stabilization of carbocations would greatly help us gain a deep understanding of the reaction mechanisms. By means of ab initio molecular dynamics (AIMD) simulations and an in situ experimental approach, a complete scrambling of 13C-labeled C4 = products was observed during the isomerization reaction in the H-ZSM5 zeolite at room temperature, and the corner-protonated methyl cyclopropanes (as a non-classical carbocation) featuring the three center two-electron (3c–2e) bonds were confirmed to be the highly active metastable intermediates of C4 isomerization. Our results not only uncover the nature of facile C shift in carbocations during zeolite-catalyzed reactions but also bring some fundamental understandings to carbocation chemistry in a zeolite confined environment 

Abstract. A new technique was used to directly measure O3 response to changes inprecursor NOx and volatile organic compound (VOC) concentrations in the atmosphere using threeidentical Teflon smog chambers equipped with UV lights. One chamberserved as the baseline measurement for O3 formation, one chamber addedNOx, and one chamber added surrogate VOCs (ethylene, m-xylene,n-hexane). Comparing the O3 formation between chambers over a3-hour UV cycle provides a direct measurement of O3 sensitivity toprecursor concentrations. Measurements made with this system at Sacramento,California, between April–December 2020 revealed that theatmospheric chemical regime followed a seasonal cycle. O3 formation wasVOC-limited (NOx-rich) during the early spring, transitioned toNOx-limited during the summer due to increased concentrations ofambient VOCs with high O3 formation potential, and then returned toVOC-limited (NOx-rich) during the fall season as the concentrations ofambient VOCs decreased and NOx increased. This seasonal pattern ofO3 sensitivity is consistent with the cycle of biogenic emissions inCalifornia. The direct chamber O3 sensitivity measurements matchedsemi-direct measurements of HCHO/NO2 ratios from the TROPOsphericMonitoring Instrument (TROPOMI) aboard the Sentinel-5 Precursor (Sentinel-5P) satellite. Furthermore, the satellite observations showed thatthe same seasonal cycle in O3 sensitivity occurred over most of theentire state of California, with only the urban cores of the very largecities remaining VOC-limited across all seasons. The O3-nonattainmentdays (MDA8 O3>70 ppb) have O3 sensitivity in theNOx-limited regime, suggesting that a NOx emissions controlstrategy would be most effective at reducing these peak O3concentrations. In contrast, a large portion of the days with MDA8 O3concentrations below 55 ppb were in the VOC-limited regime, suggesting thatan emissions control strategy focusing on NOx reduction would increaseO3 concentrations. This challenging situation suggests that emissionscontrol programs that focus on NOx reductions will immediately lowerpeak O3 concentrations but slightly increase intermediate O3concentrations until NOx levels fall far enough to re-enter theNOx-limited regime. The spatial pattern of increasing and decreasingO3 concentrations in response to a NOx emissions control strategyshould be carefully mapped in order to fully understand the public healthimplications. 

Abstract The NOAA/NASA Fire Influence on Regional to Global Environments and Air Quality (FIREX‐AQ) experiment was a multi‐agency, inter‐disciplinary research effort to: (a) obtain detailed measurements of trace gas and aerosol emissions from wildfires and prescribed fires using aircraft, satellites and ground‐based instruments, (b) make extensive suborbital remote sensing measurements of fire dynamics, (c) assess local, regional, and global modeling of fires, and (d) strengthen connections to observables on the ground such as fuels and fuel consumption and satellite products such as burned area and fire radiative power. From Boise, ID western wildfires were studied with the NASA DC‐8 and two NOAA Twin Otter aircraft. The high‐altitude NASA ER‐2 was deployed from Palmdale, CA to observe some of these fires in conjunction with satellite overpasses and the other aircraft. Further research was conducted on three mobile laboratories and ground sites, and 17 different modeling forecast and analyses products for fire, fuels and air quality and climate implications. From Salina, KS the DC‐8 investigated 87 smaller fires in the Southeast with remote and in‐situ data collection. Sampling by all platforms was designed to measure emissions of trace gases and aerosols with multiple transects to capture the chemical transformation of these emissions and perform remote sensing observations of fire and smoke plumes under day and night conditions. The emissions were linked to fuels consumed and fire radiative power using orbital and suborbital remote sensing observations collected during overflights of the fires and smoke plumes and ground sampling of fuels. 

Abstract Convective systems dominate the vertical transport of aerosols and trace gases. The most recent in situ aerosol measurements presented here show that the concentrations of primary aerosols including sea salt and black carbon drop by factors of 10 to 10,000 from the surface to the upper troposphere. In this study we show that the default convective transport scheme in the National Science Foundation/Department of Energy Community Earth System Model results in a high bias of 10–1,000 times the measured aerosol mass for black carbon and sea salt in the middle and upper troposphere. A modified transport scheme, which considers aerosol activation from entrained air above the cloud base and aerosol‐cloud interaction associated with convection, dramatically improves model agreement with in situ measurements suggesting that deep convection can efficiently remove primary aerosols. We suggest that models that fail to consider secondary activation may overestimate black carbon's radiative forcing by a factor of 2.