Using velocity map ion imaging, the photodissociation of chlorobromomethane (CH2BrCl) at 233-234 nm has been studied. The total translational energy distributions and the anisotropy parameters have been determined from the ion images of the photofragments Br ((2)P1/2) (denoted as Br(*)) and Br ((2)P3/2) (denoted as Br) for the dominant CH2BrCl + hv → CH2Cl + Br(*) and CH2BrCl + hv → CH2Cl + Br channels. Using an impulsive model invoking angular momentum conservation, the vibrational energy distributions of the chloromethyl radicals have been derived from the total translational energy distributions for the two channels. The study suggests that there are a number of vibrational modes of the chloromethyl radical to be excited in both of the two photodissociation channels. In the Br* channel, the CH2 s-stretch mode v1 has the most probability of excitation. While in the Br channel, the CH2 scissors mode ν2 is attributed to the highest peak of the vibrational energy curve of the chloromethyl radical. The results further imply that, following absorption of one UV photon of 234 nm, other vibrational modes besides v5 (C-Br stretch mode) are also excited in the parent molecule.
We theoretically study the high-order harmonic generation (HHG) from Rydberg hydrogen atom driven by a mid-infrared linearly polarized chirped laser pulse. It is shown that the high-order harmonic spectrum demonstrates an excessive high-yield broad-band supercontinuum. Based on the analyses of quantum-mechanical and classical models, it is found that the enhancement is caused by the motion of the Rydberg electron perpendicular to the polarization direction of the chirped laser pulse, which is induced by the attraction of the nucleus and initial orbital velocity of the Rydberg electron. This mechanism is different from the previous study (Chen et al 2015 Phys. Rev. A 91 043403), in which the motion of the Rydberg electron perpendicular to the polarization direction has little contribution to HHG.
Regional transport is equally significant to local sources in contributing to PM2.5 pollution and associated environmental inequality. In the context of future climate change, the effect of the responses of regional transport to the warming climate and controlling emissions has not been thoroughly investigated. Here we establish cross-province PM2.5 source-receptor matrix in China in 2015 baseline and two climate pathways in 2050s (SSP585 and SSP126), using Community Multi-scale Air Quality model embedded with the Integrated Source Apportionment Method. Results suggest that across-regional transport contributes 36.1 % - 62.3 % of PM2.5 in five severely polluted regions, which is even more important compared to inner transport within the target region (3.8 % - 19.4 %), especially in Chuanyu and Fenwei regions which are polluted by large PM2.5 transport (over 50 %) from outside regions. Such results imply that joint-control policy should not only focus on neighboring provinces. Controlling pollutant emission is undoubtedly reduced the concentration of PM2.5 regional transport (by -5.25 µg/m3 on average), largely exceeding the influence from the meteorological fluctuations (by -0.82 µg/m3 on average) driven by the climate change in 2050s. On the other hand, future controlled pollutant emissions proved that strengthen across-regional transport with an enlarged relative contribution to total PM2.5 concentration (8.46%) in 2050, along with a decreased contribution from local sources (8.54%). Therefore, environmental inequality issue should be pay more attention in the context of the reduction of pollution and carbon emissions.
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