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The Ni_n (n =19, 20) +D₂ (v, j) collision systems have been studied to investigate the dependence of cluster reactivity on the cluster temperature and the initial rovibrational states of the molecule using quasiclassical molecular dynamics simulations. The clusters are described by an embedded atom potential, whereas the interaction between the molecule and the cluster is modeled by a LEPS (London–Eyring–Polani–Sato) potential energy function. Reaction (dissociative adsorption) cross-sections are computed as functions of the collision energy for different initial rovibrational states of the molecule and for different temperatures of the clusters. Rovibrational, temperature and size-dependent rate constants are also presented, and the results are compared with earlier studies. Initial vibrational excitation of the molecule increases the reaction cross-section more efficiently than the initial rotational excitation. The reaction cross-sections strongly depend on the collision energies below 0.1 eV.

Contrary to almost standard opinion that the $X(3872$) resonance is the $D^{\ast 0}{\bar{D}}^0+\mathrm{\text{c.c.}}$ molecule or the $qc\bar{q}\bar{c}$ four-quark state, we discuss the scenario where the $X(3872)$ resonance is the $c\bar{c}={\chi }_{c1}(2P)$ charmonium which “sits on” the $D^{\ast 0}{\bar{D}}^0$ threshold.

We explain the shift of the mass of the $X(3872)$ resonance with respect to the prediction of a potential model for the mass of the ${\chi }_{c1}(2P)$ charmonium by the contribution of the virtual $D^{\ast }\bar{D}+\mathrm{\text{c.c.}}$ intermediate states into the self energy of the $X(3872)$ resonance. This allows us to estimate the coupling constant of the $X(7872)$ resonance with the $D^{\ast 0}{\bar{D}}^0$ channel, the branching ratio of the $X(3872)\to D^{\ast 0}{\bar{D}}^0+\mathrm{\text{c.c.}}$ decay, and the branching ratio of the $X(3872)$ decay into all non-$D^{\ast 0}{\bar{D}}^0+\mathrm{\text{c.c.}}$ states. We predict a significant number of unknown decays of $X(3872)$ via two gluon: $X(3872)\to \text{gluon gluon}\to \text{hadrons}$.

We suggest a physically clear program of experimental researches for verification of our assumption.

Hadron spectroscopy is revealed by observing heavy resonances. Among various explanations of the internal structure of these hadronic states, hadronic molecules play a unique role. For hadronic molecules, which are associated with meson–meson or meson–baryon interactions, the $\mathrm{\Lambda }$ cutoff is a significant factor in determining the composite states’ binding energies and overall properties. The cutoff becomes important when it comes to the location of hadronic molecules’ masses because it influences the predictions. From this perspective, in the light of cutoff dependency, heavy quark spin partners of near-threshold the ${\chi }_{c0}(3915)$, ${\chi }_{c1}(3872)$, $P_c(4440)$, and $P_c(4457)$ resonances, which are considered as hadronic molecules, are examined.

We perform a systematic study of the bound state problem of and systems by using effective interaction in our chiral quark model. Our results show that both the interactions of and states are attractive, which consequently result in and bound states.

A survey of recent Raman scattering studies on the interstitial hydrogen molecule (H₂) in Si and GaAs is presented. It is shown that properties of H₂ strongly depend on the nuclear spin state I. In either material, para-H₂ (I=0) is unstable against irradiation with band gap light. In the case of Si, para-H₂ also preferentially disappears from the Raman spectra in the course of storage at room temperature in the dark. Possible explanations for this surprising behavior are discussed and compared with the latest infrared absorption studies.

The theoretical calculation of the refractive indices is of great significance for the developments of new optical materials. The calculation method of refractive index, which was deduced from the electron-cloud-conductor model, contains the shape and direction factor $〈g〉$. $〈g〉$ affects the electromagnetic-induction energy absorbed by the electron clouds, thereby influencing the refractive indices. It is not yet known how to calculate $〈g〉$ value of non-spherical electron clouds. In this paper, $〈g〉$ value is derived by imaginatively dividing the electron cloud into numerous little volume elements and then regrouping them. This paper proves that $〈g〉=2/3$ when molecules’ spatial orientations distribute randomly. The calculations of the refractive indices of several substances validate this equation. This result will help to promote the application of the calculation method of refractive index.

We are interested in dynamics of a system in an environment, or an open system. Such phenomena as crossover from Markovian to non-Markovian relaxation and thermal equilibration are of our interest. Open systems have experimentally been studied with ultra cold atoms, ions in traps, optics, and cold electric circuits because well-isolated systems can be prepared here and thus the effects of environments can be controlled. We point out that some molecules solved in isotropic liquid are well isolated and thus they can also be employed for studying open systems in Nuclear Magnetic Resonance (NMR) experiments. First, we provide a short review on related phenomena of open systems that helps readers to understand our motivation. We, then, present two experiments as examples of our approach with molecules in isotropic liquids. Crossover from Markovian to non-Markovian relaxation was realized in one NMR experiment, while relaxation-like phenomena were observed in approximately isolated systems in the other.

We present a simple physical explanation that measurements of the collision cross-sections with pure energy resolution can provide information on the reaction dynamics equivalent to that obtained using real-time methods of femtochemistry. For nuclear collisions, the method provides a time resolution of ~ 10^-21 sec. The method is sensitive enough to distinguish between the different scenarios of rotational dephasing for the highly-excited nuclear molecules, with strongly overlapping resonances, formed in ¹²C + ²⁴Mg scattering. We find that the dephasing is much slower than the intra-molecular energy redistribution. This reveals unusual states — nonergodic molecules in continuum. Anomalously long dephasing times observed in highly-excited polyatomic molecules may reflect this new type of nonergodicity.

This paper focuses on the use and value of XPS and NEXAFS spectroscopies to unveil the nature of the chemical bond of various bifunctional nitrile molecules adsorbed on Si(001) 2×1 at 300 K. The adsorption modes are also discussed in the light of recent theoretical publications devoted to optimized geometries and reaction paths of these molecules on Si(001).

The newly observed exotic mesons above threshold were widely discussed in the molecular picture. To understand deeper their structures, we here discuss the spin () of a heavy quark-antiquark pair in an S-wave meson-antimeson system by constructing explicitly the spin wave function. One finds two selection rules for (a) the total angular momentum J is larger than the maximum angular momentum of the light degree of freedom or smaller than the minimum one; (b) J^C = 1⁺, 2^-, 3⁺, ⋯ if the two mesons are different but belong to the same doublet. This feature may be used to constrain possible strong decay channels.

The molecular approach of a spin model is constructed on the Bethe lattice (BL), and then it is examined in terms of exact recursion relations. Rather than assuming that each BL site is inhabited by a single spin, each site is occupied by two spin-1/2 atoms A and B, forming a molecule. Each molecule is considered to contain two spin-1/2 atoms, as well as $q=3,4,$ or 6 nearest-neighbor molecules. In addition to the internal interactions between the atoms of each molecule, the molecules interact via their atoms in terms of bilinear interaction parameters J. Atoms of a molecule interact with $J_{A^i{B}^i}$, while the molecules interact via their atoms in terms of $J_{A^i{B}^{i+1}}=J_{B^i{A}^{i+1}}$ and $J_{A^i{A}^{i+1}}=J_{B^i{B}^{i+1}}$. After obtaining the magnetizations of each atom in the central molecule of the BL, the average magnetization of the molecule is determined. It is found that the model presents first-and second-order and random phase transitions. The model also displays tricritical, bicritical and end points, in addition to reentrant behavior for appropriate J values.

In this paper, thermal diffusion states of pure diethyl ether and its mixture with cellulose dinitrate tripolymer were uncovered by LAMMPS-based Molecular Dynamic (MD) simulations. Those MD simulations were generally performed through specified ReaxFF reactive force field to obtain the properties of the chemical system such as molecular energy, density, mean square displacement (MSD) and molecular coordinate. The result of MD simulations presented the clear superheating phenomenon of pure liquid diethyl ether system in the studied environment. The obtained phase transition point was much higher than the reported one. The deviation between two temperatures was about 132.369K. It was also demonstrated that the transition process was associated with the sharp increment of potential energy, volume, diffusion coefficient and cohesive energy. However, the split of these diethyl ether molecules was not uniform. The cluster-like transition state was observed before the end of the vaporing process (460K). As for the addition of cellulose dinitrate tripolymer, these molecules were not agglomerated in the simulated organic mixture. However, the diffusion of cellulose dinitrate tripolymer was much weaker than those diethyl ether molecules. While the concentration of cellulose dinitrate tripolymer was higher, molecular interactions of this organic mixture were consequently improved, and this further limited the diffusion behavior of the entire chemical system. It could be concluded that the diffusion behavior of the entire organic system was decreased with more amount of cellulose dinitrate tripolymer molecules.

Photoassociation of ultracold atoms has been used to determine interaction potentials and to extract scattering lengths with great precision, which we discuss here in the context of lithium. We also describe a recent experiment where saturation in the rate of photoassociation of an atomic BEC was observed.

Recently observed heavy quark exotic XYZ mesons stimulated heated discussions about their structures. In the molecule picture, we discuss the spin of the heavy quark pair in an S-wave meson-antimeson state, whose value is either 1 or 0. We find two rules that the spin is only 1 in the heavy quark limit. From the conservation of the spin, one may analyze the charmonium products from strong decays. The selection rules give constraints on the products.