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Since the launch of the rural revitalization strategy, the heat of rural revitalization has intensified. However, the study of rural agricultural modernization or urban-rural integration development is not without the premise of rural security. Therefore, there are obstacles, this paper takes the lead in analyzing the internal and external logic of rural security, and provides a reference for realizing rural security, health and sustainable development.

The photodissociation dynamics of small (H2O)n+ (n=2–5) clusters have been studied at 308 nm using a high resolution cryogenic cylindrical ion trap velocity map imaging spectrometer. Time-of-flight mass spectra and images of ionic photofragments are recorded. (H2O)2+ clusters dissociate to yield H3O+ and H2O+ photofragments, indicating the presence of both proton-transferred (H3O+-OH) and hemibonded (H2O-OH2)+ structures for the dimer cluster. (H2O)n+ (n=3–5) clusters prevailingly dissociate to the H+(H2O)n–2, ...,1 photofragments by losing both of OH and H2O components, and the (H2O)5+ cluster shows an additional channel to produce H+(H2O)4 by only losing OH. The former suggests the (H2O)n–2H3O+OH structures for the (H2O)n+ (n=3–5) clusters, while the latter suggests in (H2O)5+ that, the H3O+ core and OH are separated by H2O. The results elucidate the structure progresses of small (H2O)n+ clusters. The experimental images yield negative and small values for the anisotropy parameters of photofragments, indicating that (H2O)n+ (n=2–5) clusters undergo vertical electronic transitions upon photon absorption followed by slow dissociation, and lead to highly internally excited photofragments. [ABSTRACT FROM AUTHOR]

Thanks to their specific molecular symmetry, aromatic molecules and their derivatives represent ideal model systems in understanding photo-induced chemistry of small molecules. Herein, ultraviolet photodissociation dynamics of the 1-bromo-2,6-difluorobenzene molecule has been visualized via imaging the recoiling velocity distributions of photofragments. The measured recoiling angular distributions of the Br(2P3/2) product vary significantly with the increasing photon energy, arguing against the simple bond-fission mechanism within the C2v symmetry. Ab initio calculations reveal that in addition to the C–Br bond cleavage, two additional internal molecular coordinates that break the molecular symmetry are likely involved. The Br out-of-plane bending opens a direct dissociation pathway on the S1-1A″ (S1-1ππ*) state, while the asymmetric C–F stretching significantly changes the orientation of the transition dipole moment. The present study sheds new light on the effect of symmetry breaking in the photodissociation dynamics of symmetric aryl halides, highlighting the multi-dimensional feature of excited state potential energy surfaces. [ABSTRACT FROM AUTHOR]

We present an experimental study on the photodissociation dynamics of [O 2 -H 2 O] + in the 580-266 nm wavelength range using a cryogenic ion trap velocity map imaging spectrometer. The cryogenic ion trap produces mass selected and internally cold [ O 2 - H 2 O ] + ions for photodissociation. By detecting both the O 2 + and H 2 O + photofragments using the time-of-flight mass spectrometry and velocity map imaging techniques, branching ratios and total kinetic energy release distributions of the O 2 + + H 2 O and H 2 O + + O 2 product channels are experimentally measured at 16 different excitation energies. State-resolved photodissociation mechanisms of the parent [O 2 -H 2 O] + are interpreted as (1) the O 2 (X 3 Σ g - ) + H 2 O + ( X ~ 2 B 1 ) , O 2 (a 1 Δ g ) + H 2 O + ( X ~ 2 B 1 ) , and O 2 (X 3 Σ g - ) + H 2 O + ( A ~ 2 A 1 ) channels are produced from direct dissociation of [O 2 -H 2 O] + in its excited B ~ 2 A ″ , D ~ 2 A ″ , and F ~ 2 A ″ states, respectively; (2) the O 2 + (X 2 Π g ) + H 2 O ( X ~ A 1 1 ) channel is produced from nonadiabatic relaxations of the excited B ~ 2 A ″ , D ~ 2 A ″ , and F ~ 2 A ″ states to the X ~ 2 A ″ ground state with subsequent dissociation. The latter nonadiabatic processes involve charge-transfer on the potential energy surfaces, and the charge-transfer probabilities are determined from experimental results. The dissociation energy of the ground state to the lowest dissociation limit is experimentally refined as D 0 = 1.05 ± 0.05 eV. This work provides important information to understand the charge-transfer dynamics in the photochemistry of [O 2 -H 2 O] + and in the ion-molecule reaction O 2 + H 2 O + → O 2 + + H 2 O.