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New expressions for the wavelength-dependent photolysis quantum yields of CH.sub.2 O, Φ.sub.j, are presented. They are based on combinations of functions of the type A.sub.i /(1+exp[−(1/λ − 1/λ.sub.0i )/b.sub.i ]). The parameters A.sub.i, b.sub.i, and λ.sub.0i which have a physical meaning, are obtained by fits to the measured Φ.sub.j data available from literature. The altitude dependence of the photolysis frequencies resulting from the new quantum yield expressions are compared to those derived from the Φ.sub.j recommended by JPL and IUPAC.

Rate coefficients, k, for the gas-phase reaction of CH3 COCHO (methylglyoxal) with the OH and NO3 radicals and (CHO)2 (glyoxal) with the NO3 radical are reported. Rate coefficients for the OH + CH3 COCHO (k1 ) reaction were measured under pseudo-first-order conditions in OH as a function of temperature (211-373 K) and pressure (100-220 Torr, He and N2 bath gases) using pulsed laser photolysis to produce OH radicals and laser induced fluorescence to measure its temporal profile. k1 was found to be independent of the bath gas pressure with k1 (295 K) = (1.29 ± 0.13) × 10-11 cm3 molecule-1 s-1 and a temperature dependence that is well represented by the Arrhenius expression k1 (T) = (1.74 ± 0.20) × 10-12 exp[(590 ± 40)/T] cm3 molecule-1 s-1 where the uncertainties are 2σ and include estimated systematic errors. Rate coefficients for the NO3 + (CHO)2 (k3 ) and NO3 + CH3 COCHO (k4 ) reactions were measured using a relative rate technique to be k3 (296 K) = (4.0 ± 1.0) × 10-16 cm3 molecule-1 s-1 and k4 (296 K) = (5.1 ± 2.1) × 10-16 cm3 molecule-1 s-1 . k3 (T) was also measured using an absolute rate coefficient method under pseudo-first-order conditions at 296 and 353 K to be (4.2 ± 0.8) × 10-16 and (7.9 ± 3.6) × 10-16 cm3 molecule-1 s-1 , respectively, in agreement with the relative rate result obtained at room temperature. The atmospheric implications of the OH and NO3 reaction rate coefficients measured in this work are discussed.

Cryogenic anion photoelectron spectroscopy combined with quantum chemical calculations was employed to investigate the electronic structures and photodetachment properties of TeO[sub.2] [sup.−], TeO[sub.3] [sup.−], and HTeO[sub.4] [sup.−] anions. The adiabatic/vertical detachment energies (ADEs/VDEs) of these anions were determined through the photoelectron spectra at 193 nm, yielding values of 2.13/1.94, 4.20/3.64, and 5.64/5.20 eV, respectively. These results align well with the theoretical calculations and were further validated through Franck–Condon factor (FCF) simulations. TeO[sub.2] [sup.−] and TeO[sub.3] [sup.−] exhibit a notable multi-reference character, with TeO[sub.3] [sup.−] showing a pronounced structural change upon detachment from C[sub.3v] to D[sub.3h] geometry, leading to a substantial difference between its ADE and VDE. Orbital analyses of the photodetachment processes reveal a progressive shift in the primary contribution to the detached electron—from the Te atom to the O atoms—as the anion size increases. Moreover, a two-photon photodissociation–photodetachment process was identified for HTeO[sub.4] [sup.−]. These findings provide fundamental insights into the geometric and electronic structures of gas-phase tellurium oxides, offering a benchmark for further theoretical modeling and material development involving chalcogen oxide anions.

The termolecular reactions of hydroxyl radicals (OH) with carbon monoxide (CO), nitric oxide (NO), and nitrogen dioxides (NO.sub.2) and the termolecular reaction of hydroperoxy radicals (HO.sub.2) with NO.sub.2 greatly impact the atmospheric oxidation efficiency. Few studies have directly measured the pressure-dependent rate coefficients in air at 1 atm pressure and water vapour as third-body collision partners. In this work, rate coefficients were measured with a high accuracy (<5 %) at 1 atm pressure, at room temperature, and in humidified air using laser flash photolysis and detection of the radical decay by laser-induced fluorescence. The rate coefficients derived in dry air are (2.39±0.11)x10-13 cm.sup.3 s.sup.-1 for the OH reaction with CO, (7.3±0.4)x10-12 cm.sup.3 s.sup.-1 for the OH reaction with NO, (1.23±0.04)x10-11 cm.sup.3 s.sup.-1 for the OH reaction with NO.sub.2, and (1.56±0.05)x10-12 cm.sup.3 s.sup.-1 for the HO.sub.2 reaction with NO.sub.2 . For the OH reactions with CO and NO, no dependence on water vapour was observed for the range of water partial pressures tested (3 to 22 hPa), and for NO.sub.2, only a weak increase of 3 % was measured, in agreement with the study by Amedro et al. (2020). For the rate coefficient of HO.sub.2 with NO.sub.2 an enhancement of up to 25 % was observed. This can be explained by a faster rate coefficient of the reaction of the HO.sub.2 -water complex with NO.sub.2 having a value of (3.4±1.1)x10-12 cm.sup.3 s.sup.-1.

We derive the upper limit on the dark matter (DM) fraction in primordial black holes (PBHs) in the mixed DM scenarios. In this scenarios, a PBH can accrete weakly interacting massive particles (WIMPs) to form a ultracompact minihalo (UCMH) with a density profile of [Formula omitted]. The energy released from UCMHs due to dark matter annihilation has influence on the photodissociation of [Formula omitted], producing the [Formula omitted] and the D. By requiring that the ratio [Formula omitted] caused by UCMHs does not exceed the measured value, we derive the upper limit on the dark matter fraction in PBHs. For the canonical value of DM thermally averaged annihilation cross section [Formula omitted], we find that the upper limit is [Formula omitted] for DM mass [Formula omitted]. Compared with other limits obtained by different astronomical measurements, although our limit is not the strongest, we provide a different way of constraining the cosmological abundance of PBHs.

Photochemical ozone (O.sub.3) pollution remains a persistent environmental challenge, and growing evidence highlights the critical role of oxygenated volatile organic compounds (OVOCs) in photochemical processes. However, comprehensive and quantitative measurements of OVOCs remain limited. This study investigates the impact of OVOCs on O.sub.3 formation mechanisms and radical budgets by intergrating high-resolution field measurements from a subtropical coastal region in South China with observation-based photochemical modeling. 63 OVOC species were measured by a proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS), and accounted for 72 %-77 % of total VOC concentrations. The O.sub.3 -precusor relationship analysis revealed a transition regime for O.sub.3 formation and high sensitivity to OVOCs. OVOC-related reactions, including OVOC photolysis, OVOC oxidation by OH and NO.sub.3 radicals, contributed approximately 36 %-73 % to daytime production rates of HO.sub.2 and RO.sub.2 radicals. Model simulations without comprehensive consideration of OVOCs would significantly underestimate daytime production rates of O.sub.3 and RO.sub.x radicals by 41 %-48 %, and shift the diagnosis of O.sub.3 formation from a transition regime to a VOC-limited regime, leading to biased policy recommendations and potentially ineffective control strategies. These findings underscore the critical role of OVOCs in atmospheric photochemistry and highlight the urgent need for comprehensive OVOC quantification to improve OVOC-inclusive model frameworks. Such improvements are essential for accurately characterizing O.sub.3 -precursor relationships and for developing effective and sustainable strategies to mitigate regional O.sub.3 pollution.

Signatures of mass‐independent fractionation (MIF) of sulfur in Archean sulfide and sulfate minerals are widely thought to record an anoxic early Earth’s atmosphere. While experiments of ultraviolet irradiation of SO2 produce significant sulfur mass‐independent fractionation (S‐MIF) in reaction products (elemental sulfur and residual sulfur dioxide), they have not been able to reproduce the isotope patterns, in particular Δ36S/Δ33S ratios, observed in the geologic rock record. Studies that focused on organic sulfur gases and hazes in Archean did not report organosulfur aerosol photoproducts as major contributors to Archean S‐MIF chemistry. Here we show, for the first time, that photochemical reactions of SO2 in the presence of gaseous hydrocarbons (CH4, C2H2, and C2H4) produce haze‐like organosulfur aerosols bearing S‐MIF with variable Δ36S/Δ33S ratios. The isotope trends for the organosulfur photoproducts produced in our experiments suggest that in addition to elemental sulfur, organosulfur compounds—in particular methanesulfonic acid—are a key component of S‐MIF signals from the atmosphere to the ocean and sediments with possible links to Archean atmosphere warmed by a methane greenhouse. Plain Language Summary Experimental ultraviolet irradiation of SO2 demonstrably induces an anomalous or mass‐independent fractionation of sulfur (S‐MIF) as evidence of an irreversible rise in atmospheric oxygen at ca. 2.4 Ga. Hitherto, such in vitro approaches did not completely confirm the variation in the S‐MIF archived in early Earth’s rock record. Here, we show that the photolysis of SO2 in the presence of reduced hydrocarbon gases produced haze‐like organosulfur aerosol photoproducts that are thought to be strongly modulated by early Earth’s atmospheric sulfur cycling and its role in S‐MIF transfer and preservation in Archean sedimentary rock record. Key Points The SO2‐CH4 photoproducts exhibit negative Δ36S/Δ33S slopes of −1.9 that is closer to the Archean reference fractionation window

The superoxide anion radical (O 2 •− ) is one of the most predominant reactive oxygen species (ROS), which is also involved in diverse chemical and biological processes. In this study, O 2 •− was generated by irradiating riboflavin in an O 2 -saturated solution using an ultraviolet lamp ( λ em = 365 nm) as the light source. The photochemical reduction of 1,4-benzoquinone ( p -BQ) by O 2 •− was explored by 355-nm laser flash photolysis (LFP) and 365-nm UV light steady irradiation. The results showed that the photodecomposition efficiency of p -BQ was influenced by the riboflavin concentration, p -BQ initial concentration, and pH values. The superoxide anion radical originating from riboflavin photolysis served as a reductant to react with p -BQ, forming reduced BQ radicals (BQ •− ) with a second-order rate constant of 1.1 × 10 9 L mol −1 s −1 . The main product of the photochemical reaction between p -BQ and O 2 •− was hydroquinone (H 2 Q). The present work suggests that the reaction with O 2 •− is a potential transformation pathway of 1, 4-benzoquinone in atmospheric aqueous environments.

Spectroscopic measurements of atmospheric trace gases, for example, by differential optical absorption spectroscopy (DOAS), are frequently supported by recording the trace-gas column density (CD) in absorption cells (cuvettes), which are temporarily inserted into the light path. The idea is to verify the proper functioning of the instruments, to check the spectral registration (wavelength calibration and spectral resolution), and to perform some kind of calibration (absolute determination of trace-gas CDs). In addition, trace-gas absorption cells are a central component in gas correlation spectroscopy instruments. In principle DOAS applications do not require absorption-cell calibration; however, in practice, measurements with absorption cells in the spectrometer's light path are frequently performed.

Halogenated disinfection by-products such as 2,6-dichlorobenzoquinone (DCBQ) are emerging microcontaminants of concern due to their persistence and toxicity in aquatic environments. This study evaluated the oxidative degradation of DCBQ under UV irradiation, focusing on the effect of H[sub.2]O[sub.2] dosage on removal efficiency and water quality. Batch experiments were conducted with H[sub.2]O[sub.2] concentrations ranging from 0.0 to 10.0 mM. Kinetic analysis revealed that photolysis with UV alone followed an apparent order of 1.5, while the UV/H[sub.2]O[sub.2] system showed an order of 2.5, reflecting the contribution of hydroxyl radicals and their dependence on both DCBQ and H[sub.2]O[sub.2] concentrations. Color evolution displayed a series reaction behavior: the initial formation of chromophoric by-products followed first-order kinetics, whereas their subsequent removal proceeded with zero-order kinetics, consistent with radical-driven decolorization. Optimal performance was achieved with 1.0–2.0 mM H[sub.2]O[sub.2], which promoted rapid DCBQ decay and significant reductions in aromaticity and color (100% in 2 h), whereas higher concentrations (10.0 mM) led to radical scavenging and lower efficiency. Dissolved oxygen increased during treatment, confirming oxidative pathways, while turbidity remained stable between 1 and NTU. These results demonstrate the effectiveness of UV/H[sub.2]O[sub.2] for DCBQ removal and highlight the value of kinetic modeling in optimizing advanced oxidation processes for water treatment.