Geometric Phase Effects in the H + H2+ Reaction on the Lowest Triplet Ground State.

To our knowledge, this is the first time geometric phase (GP) effects in the H + H2+ reaction on its lowest triplet ground state with collision energies lower than 1.85 eV have been studied using the quantum wave packet method and vector potential approach. We obtained the total reaction probabilities including and not including GP (NGP) effects for J ≤ 4. Visible GP effects could be seen at the lower energy regime but are tiny at the higher one. Moreover, they are more obvious in the product rovibrational state-resolved reaction probabilities, and the relative resonance magnitudes between GP and NGP results change with product rotational state values alternatively. The main reasons are the interferences between the one- and two-transition-state (1-TS and 2-TS) reaction paths, in that at the lower energy regime, the reaction probabilities from the 2-TS pathway show peaks of comparable probabilities compared with that of the 1-TS pathway. In addition, the "out-of-phase" trend observed in the H + H2 reaction does not exist rigorously in this system. Importantly, the visible GP effects exist in this H3+ system, which makes it a very useful candidate reaction for nonadiabatic investigations in both theory and experiment.

Control of the fluorescence molecule 2-(2'-hydroxyphenyl) benzothiazole derivatives by introducing electron-donating and withdrawing substituents groups.

Using density functional theory (DFT) and time-dependent density functional theory (TDDFT), we investigate the fluorescence mechanism of (E)-4-(3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methylstyryl)-1-methylpyridin-1-ium (HBTMY) and the excited-state intramolecular proton transfer process (ESIPT) of hydroxyphenyl. Herein, we introduce two electron-donating (amino and methoxy) and two electron-withdrawing (hydrogen and cyano) groups into HBTMY to study their effects on the fluorescence and the ESIPT process. Structural parameters, infrared vibration frequency, vertical excitation and emission energies as well as frontier molecular orbitals show that the substituents have different impacts on intramolecular hydrogen bonding behavior. The result shows that the fluorescence wavelength of molecules with the amino group could reach the near-infrared area, which favors using this fluorescence in the living cell. As the ability of electron-absorbing groups increases, the forward energy barrier in the potential energy curves decreases sharply making the ESIPT process more familiar to take place. Thus, this work offers a guide for cell imaging and provides strategies to adjust and control fluorescence by introducing substituents.

The two-pronged approach of heteroatoms and substituents to achieve a synergistic regulation of the ESIPT process in amino 2-(2'-hydroxyphenyl)benzoxazole derivatives.

Amino 2-(2'-hydroxyphenyl)benzazole derivatives are a class of molecules with excellent photophysical properties. Most of them can be applied as a fluorescent probe via the excited-state intramolecular proton transfer (ESIPT) process. In this work, we focus on the effects of heteroatoms (O, S) and substituents (acetylacetone, hydrogen) in the derivatives. Using DFT/TDDFT methods with the B3LYP-D3BJ functionals, the absorption and emission peaks are in good agreement with the experimental data. Results of optimized structures, infrared vibrational spectra, and reduced density gradient present the existence of the ESIPT process in the S1 state in these molecules, it also indirectly shows that the heteroatom S is more than O, and the substituent acetylacetone is more than hydrogen has stronger hydrogen bonds. The proton transfer (PT) potential energy curves (PECs) qualitatively show that it is easier for the heteroatom S to induce ESIPT than that of O. The same for the substituent acetylacetone than that of hydrogen. Under the joint influence of the simultaneous stacking of heteroatom S and acetylacetone substituent, the energy barrier of the PT process can be effectively lowered, realizing a synergistic strategy, which can provide some guidance for the design of fluorescent materials.

Colloidal Synthesis and Charge-Carrier Dynamics of Cs2 AgSb1-y Biy X6 (X: Br, Cl; 0 ≤y ≤1) Double Perovskite Nanocrystals.

A series of lead-free double perovskite nanocrystals (NCs) Cs2 AgSb1-y Biy X6 (X: Br, Cl; 0≤y≤1) is synthesized. In particular, the Cs2 AgSbBr6 NCs is a new double perovskite material that has not been reported for the bulk form. Mixed Ag-Sb/Bi NCs exhibit enhanced stability in colloidal solution compared to Ag-Bi or Ag-Sb NCs. Femtosecond transient absorption studies indicate the presence of two prominent fast trapping processes in the charge-carrier relaxation. The two fast trapping processes are dominated by intrinsic self-trapping (ca. 1-2 ps) arising from giant exciton-phonon coupling and surface-defect trapping (ca. 50-100 ps). Slow hot-carrier relaxation is observed at high pump fluence, and the possible mechanisms for the slow hot-carrier relaxation are also discussed.

Accurate Quantum Wave Packet Study of the Deep Well D+ + HD Reaction: Product Ro-vibrational State-Resolved Integral and Differential Cross Sections.

The H+ + H2 reaction and its isotopic variants as the simplest triatomic ion-molecule reactive system have been attracting much interests, however there are few studies on the titled reaction at state-to-state level until recent years. In this work, accurate state-to-state quantum dynamics studies of the titled reaction have been carried out by a reactant Jacobi coordinate-based time-dependent wave packet approach on diabatic potential energy surfaces constructed by Kamisaka et al. Product ro-vibrational state-resolved information has been calculated for collision energies up to 0.2 eV with maximal total angular momentum J = 40. The necessity of including all K-component for accounting the Coriolis coupling for the reaction has been illuminated. Competitions between the two product channels, (D+ + HD' → D'+ + HD and D+ + HD' → H+ + DD') were investigated. Total integral cross sections suggest that resonances enhance the reactivity of channel D+ + HD'→ H+ + DD', however, resonances depress the reactivity of the another channel D+ + HD' → D'+ + HD. The structures of the differential cross sections are complicated and depend strongly on collision energies of the two channels and also on the product rotational states. All of the product ro-vibrational state-resolved differential cross sections for this reaction do not exhibit rigorous backward-forward symmetry which may indicate that the lifetimes of the intermediate resonance complexes should not be that long. The dynamical observables of this deuterated isotopic reaction are quite different from the reaction of H+ + H2 → H2 + H+ reported previously.

Dissociation and ionization competing processes for H2+ in intense laser field: which one is larger?

Competition between dissociation and ionization of H(2)(+) in intense laser field has been investigated by using an accurate three-dimensional time-dependent wavepacket approach. The disagreement between the experiment and the former one-dimensional theory has been resolved. In a comparison of the calculated results with the available experimental data, a good agreement is reached, not only for the relative probabilities between dissociation and ionization but also for the two-peak structures and the peak energy locations for these two processes.