Molecular Bound State Research Articles

Dynamical study of D*DK and D*DD¯ systems at quark level

Inspired by the recent report from the LHCb Collaboration on Tcc, which can be interpreted as a molecular DD*, we investigated two trimeson systems of the Tcc partner with IJP=01− in the framework of a chiral quark model. In the first case, because of the attraction between D* and D¯, we explored the existence of bound states in the system D*DD¯, which is obtained by adding D¯ into the molecular bound state Tcc (DD*). Similarly, in the second case, we explored whether there is a bound state in the D*DK system, which is obtained by adding K into the Tcc, given the attraction between D and K. The results show that both of them are bound states, in which the binding energy of the molecular state DD*K is relatively small, only 0.4±0.4 MeV, while the binding energy of DD*D¯ is up to 1.6±0.3 MeV. According to the calculation results of the root-square-mean distances, the spatial structure of the two systems shows the obvious (DD*)−(D¯/K) structure, in which D is close to D* while DD* as a whole is relatively distant from the third hadron (D¯/K), which are similar to the nucleon-electron structure. As a result, we strongly recommend that these bound states DD*D¯ and DD*K are searched for experimentally. Published by the American Physical Society 2024

On-Surface Synthesis and Spectroscopy of Aluminum Phthalocyanine on Superconducting Lead.

Large ordered islands of aluminum phthalocyanine (AlPc) molecules, which are unstable in air, are synthesized from ClAlPc on Pb(100) via dechlorination. Low-temperature scanning tunneling microscopy reveals that isolated AlPc molecules lose their spin moment on superconducting Pb(100). Molecular magnetism, which is detected via Yu-Shiba-Rusinov (YSR) resonances, may be restored by surrounding a molecule with an array of neighbor molecules in artificial arrays or in a self-assembled monolayer. Unlike phthalocyanine (H2Pc) or lead phthalocyanine (PbPc) monolayers, where the YSR energy was found to depend strongly on the detailed configuration of the neighboring molecules, we find a similar magnetic moment on every second molecule for AlPc. In addition, YSR resonances lead to unusually high conductance peaks that are due to vibrational excitations. Twelve vibrational modes are resolved and discussed with respect to similar results from PbPc. The enhancement of the inelastic transitions is tentatively attributed to the large amplitude of the YSR resonances and the long lifetime of electrons in the molecular bound state. By assembling neighboring molecules into configurations that differ from those of the monolayer, the YSR energy may be fine-tuned, and a simple spin-state switching device is constructed.

Evidence supporting the existence of Pc(4380)± from the recent measurements of Bs→J/ψpp¯

Very recently, the LHCb collaboration released the newest measurements of $B_s \to J/\psi p\bar{p}$, where an enhancement structure near 4.34 GeV was observed in the invariant mass spectrum of $J/\psi p$ with the statistical significance of $3.1-3.7$ $\sigma$. In this work, by performing a combined analysis for the three invariant mass spectra of $B_s \to J/\psi p\bar{p}$, we find that this $J/\psi p$ structure near 4.34 GeV can correspond to the contributions from the $P_c(4380)^+$ state with the assumption of $J^{P}=3/2^{-}$ together with the reflections of $B_s \to (f_2^{*} \to p\bar{p})J/\psi$. Here, $P_c(4380)$ was first observed in $\Lambda_b \to J/\psi p K$ but not confirmed in the updated LHCb data in 2019, and $f_2^{*}$ means the exciting light isoscalar tensor meson around 2.0 GeV. Thus, this provides a possible evidence to support the existence of the pentaquark $P_c(4380)$. Specifically, the assumed spin parity $J^{P}=3/2^{-}$ of $P_c(4380)$ is consistent with a prediction of the theoretical explanation of an $S$-wave $\bar{D}\Sigma_c^*$ molecular bound state.

Two particles on a chain with disordered interaction: Localization and dissociation of bound states and mapping to chaotic billiards

We consider two particles hopping on a chain with a contact interaction between them. At strong interaction, there is a molecular bound state separated by a direct gap from a continuous band of atomic states. Introducing weak disorder in the interaction, the molecular state becomes Anderson localized. At stronger disorder, part of the molecular band delocalizes and dissociates due to its hybridization to the atomic band. We characterize these different regimes by computing the density of states, the inverse participation ratio, the level-spacing statistics and the survival probability of an initially localized state. The atomic band is best described as that of a rough billiard for a single particle on a square lattice that shows signatures of quantum chaos. In addition to typical "chaotic states", we find states that are localized along only one direction. These "separatrix states" are more localized than chaotic states, and similar in this respect to scarred states, but their existence is due to the separatrix iso-energy line in the interaction-free dispersion relation, rather than to unstable periodic orbits.

The explanation of some exotic states in the cs{bar{c}}{bar{s}} tetraquark system

Inspired by the recent observation of chi _{c0}(3930), X(4685) and X(4630) by the LHCb Collaboration and some exotic resonances such as X(4350), X(4500), etc. by several experiment collaborations, the cs{bar{c}}{bar{s}} tetraquark systems with J^{PC}=0^{++}, 1^{++}, 1^{+-} and 2^{++} are systematically investigated in the framework of the quark delocalization color screening model(QDCSM). Two structures, the meson–meson and diquark–antidiquark structures, as well as the channel-coupling of all channels of these two configurations are considered in this work. The numerical results indicate that the molecular bound state D^{-}_{s}D_{s}^{+} with J^{PC}=00^{++} can be supposed to explain the chi _{c0}(3930). Besides, by using the stabilization method, several resonant states are obtained. Among these states, X(4350), X(4500) and X(4700) can be explained as the compact tetraquark states with J^{PC}=00^{++}, and the X(4274) is possible to be a candidate of the compact tetraquark state with J^{PC}=1^{++}. Apart from that, the J^{PC}=0^{++} resonance state with energy range 4028–4033 MeV, the two J^{PC}=2^{++} resonance states with energy range of 4394–4448 MeV and 4526–4536 MeV are possible to be new exotic states, which are indeed worthy of attention. More experimental tests are expected to check the existence of all these possible resonance states.

Long-Range Atom–Ion Rydberg Molecule: A Novel Molecular Binding Mechanism

We present a novel binding mechanism where a neutral Rydberg atom and an atomic ion form a molecular bound state at a large internuclear distance. The binding mechanism is based on Stark shifts and level crossings that are induced in the Rydberg atom due to the electric field of the ion. At particular internuclear distances between the Rydberg atom and the ion, potential wells occur that can hold atom–ion molecular bound states. Apart from the binding mechanism, we describe important properties of the long-range atom–ion Rydberg molecule, such as its lifetime and decay paths, its vibrational and rotational structure, and its large dipole moment. Furthermore, we discuss methods of how to produce and detect it. The unusual properties of the long-range atom–ion Rydberg molecule give rise to interesting prospects for studies of wave packet dynamics in engineered potential energy landscapes.

PHASE TRANSITIONS IN THE DEBRIS FLOW GEOSYSTEMS

The evolution of a geosystem can be described as a continuous process. Stages of geosystems evolution: the formation of a massif of loose rocks in a site, its transformation to potential massifs due to diagenesis and morphogenesis, the occurrence and movement of a debris flow, unloading of large-block and then – fine-dispersed material and the passage of a debris-flow. Each stage of the geosystem evolution can be described as a transition from one subsystem level to another and the change of states of the system – as phase transitions of first kind. Physical processes occurring within the system cause it. The most important transition is from a solid state (potential debris-flows massif-conditionally homogeneous solid having an internal structure) to a and mudflow (quasi-liquid state). The transition of a potential massif to another phase state is due not only to external factors (the inflow of free water into the site), but also internal: the mineralogical composition of rocks of the potential massif (the content of hydrophilic minerals). The most important parameter that determines both the connectivity of the soils of the potential massif and the conditions of its transition to the liquid phase are the electric forces at the contacts between the elements of the mineral skeleton (soil particles). Electrical forces provide a connection between the ground particles. The liquid component of the mudflow is traditionally described as a debris-flow suspension, but a coherent and mudflow is not a suspension. A suspension is a dispersed system consisting of a solid dispersed phase and a liquid dispersion medium in which the solid is uniformly distributed as minute particles in a liquid substance in suspension. Such a medium is not able to carry over long distances block-boulder material having a higher density than the suspension. Nevertheless, a coherent and mudflow is a conditionally single-phase system in which water is predominantly in a molecular bound state. The physical analogue of a coherent and mudflow is a colloidal system, since in a connected village fine-earth particles are distributed in a continuous dispersion medium and do not precipitate. This circumstance is key in the physical modeling of connected debris-flows and mudflows.

Production of ultracold 85Rb133Cs molecules in the lowest ground state via the B1Π1 short-range state.

We investigate the production of cold 85Rb133Cs molecules in the lowest vibronic level of the ground electronic state via the B1Π1 short-range state. The photoassociation (PA) spectra of the B1Π1 state, including newly observed transition to 2 vibronic levels, are obtained by high sensitivity time-of-flight mass spectrometry. Based on these PA spectra, the harmonic and anharmonic constants of vibronic states are obtained, resulting in predicted vibronic energies with an uncertainty of 1-2 cm-1. The B1Π1 (v = 3) state is found to have the maximum production rate for ground-state molecules with a value of 3(1) × 104 s-1, which is 3 times larger than the value via the previously studied 23Π0+ (v = 10, J = 0) state with two-photon cascade decay. The populations of J = 0, 1, and 2 rotational levels of X1Σ+ (v = 0) state molecules formed via the B1Π1 (v = 3, J = 1) state are measured to be around 20%, 40%, and 20%. To quantify the coupling strength between the B1Π1 (v = 3) state and X1Σ+ (v = 0) state, the transition dipole moment between them is measured to be 7.2(2) × 10-3ea0, which is also 3 times larger than the value between the 23Π0+ (v=10) state and X1Σ+ (v = 0) state, meaning the B1Π1 (v = 3) state has a stronger coupling with the X1Σ+ (v = 0) state. Our detailed measurements provide relevant parameters for investigation on direct stimulated Raman adiabatic passage transfer between the atomic scattering state and molecular bound state for 85Rb133Cs molecules.

Molecular Assembly of Ground-State Cooled Single Atoms

We demonstrate full quantum state control of two species of single atoms using optical tweezers and assemble the atoms into a molecule. Our demonstration includes 3D ground-state cooling of a single atom (Cs) in an optical tweezer, transport by several microns with minimal heating, and merging with a single Na atom. Subsequently, both atoms occupy the simultaneous motional ground state with 61(4)\% probability. This realizes a sample of exactly two co-trapped atoms near the phase-space-density limit of one, and allows for efficient stimulated-Raman transfer of a pair of atoms into a molecular bound state of the triplet electronic ground potential $a^3\Sigma^+$. The results are key steps toward coherent creation of single ultracold molecules, for future exploration of quantum simulation and quantum information processing.

Polaritonic Cross Feshbach Resonance.

We demonstrate the existence of a cross Feshbach resonance by strongly driving a lower polariton mode and by monitoring in time the transmission of a short optical pulse at the energy of the upper polariton mode in a semiconductor microcavity. From the signatures of the optical resonance, strength, and sign of the energy shift, we attribute the origin of the scattering process between polariton modes with opposite circular polarization to a biexciton bound state. From this study, we infer the conditions required for a strong enhancement of the generation of entangled photon pairs.

X(3872) as a molecular DD¯* state in the Bethe-Salpeter equation approach

We discuss the possibility that the X(3872) can be a $D\bar{D}^*$ molecular bound state in the Bethe-Salpeter equation approach in the ladder and instantaneous approximations. We show that the $D\bar{D}^*$ bound state with quantum numbers $J^{PC}=1^{++}$ exists. We also calculate the decay width of $X(3872) \rightarrow \gamma J/\psi$ channel and compare our result with those from previous calculations.

The mass spectra and decay properties of dimesonic states, using the Hellmann potential

Mass spectra of the dimesonic (meson-antimeson) molecular states are computed using the Hellmann potential in variational approach, which consists of relativistic correction to kinetic energy term as well as to the potential energy term. For the study of molecular bound state system, the Hellmann potential of the form $V(r)=-\frac{\alpha_{s}}{r} + \frac{B e^{-Cr}}{r}$ is being used. The one pion exchange potential (OPEP) is also incorporated in the mass calculation. The digamma decay width and decay width of the dimesonic system are evaluated using the wave function. The experimental states such as $f_{0}(980)$, $b_{1}(1235)$, $h_{1}(1380)$, $a_{0}(1450)$, $f_{0}(1500)$, $f_{2}'(1525)$,$f_{2}(1565)$, $h_{1}(1595)$, $a_{2}(1700)$, $f_{0}(1710)$, $f_{2}(1810)$ are compared with dimesonic states. Many of these states (masses and their decay properties) are close to our theoretical predictions.

Mass scaling in photoassociation of spin-singlet atoms

SynopsisPhotoassociation spectroscopy, based on forming of molecules from colliding atoms in the presence of light, is a priceless tool for the study of atomic interactions. It enables direct measurements of bound state energies, both in excited and ground state molecules. Applications include determinations of s-wave scattering lengths, as well as atomic state lifetimes. In this work we present the results of our research on the mass-scaling behaviour of molecular bound state energies and collisional properties in spin-singlet atoms. We will concentrate on two such species: strontium and ytterbium, both of which offer several stable isotopes, enabling mass tuning of the system's properties.

X(3915)as aDsD¯sbound state

We suggest that the observed properties of the charmoniumlike resonance $X(3915)$ can possibly be explained if it is an $S-$wave molecular bound state of $D_s \bar D_s$ meson pair with binding energy about 18\,MeV. In particular, the decays of $X(3915)$ to pairs of non-strange $D$ mesons are suppressed and proceed at a rate comparable to that of the decay $X(3915) \to \omega J/\psi$, whose branching fraction can be as large as about 0.3. Other major types of decay of $X(3915)$ with a comparable (or slightly smaller) rate are the transition $X(3915) \to \eta \eta_c$ and the decays into light hadrons due to the annihilation of the $c \bar c$ quark pair. The existence of a bound state should lead to an enhancement in the spectrum of the invariant mass for the $D_s \bar D_s$ near threshold in $B$ decays, e.g. in $B \to K D_s \bar D_s$ which enhancement can be tested experimentally.

X(3872)production in high energy heavy ion collisions

We have determined the production cross sections of the $X(3872)$ state in the reactions $\bar D D\to\pi X$, $\bar D^* D\to \pi X$ and $\bar D^* D^*\to\pi X$, information which is useful for studies of the $X(3872)$ meson abundance in heavy ion collisions. We construct a formalism considering $X$ as a molecular bound state of $\bar D^0 D^{*0} - \textrm{c.c}$, $D^- D^{*+} - \textrm{c.c}$ and $D^-_s D^{*+}_s - \textrm{c.c}$. To obtain the amplitudes related to these processes we have made use of effective field Lagrangians. The evaluation of the cross section of the processes involving $D^*$ meson(s) requires the calculation of an anomalous vertex, $X\bar D^* D^*$, which has been obtained by considering triangular loops motivated by the molecular nature of $X(3872)$. Proceeding in this way, we have evaluated the cross section for the reaction $\bar D^* D\to \pi X$, and find that the diagrams involving the $X\bar D^* D^*$ vertex give a large contribution. Encouraged by this finding we estimate the $X\bar D^* D^*$ coupling, which turns out to be $1.95\pm 0.22$. We then use it to obtain the cross section for the reaction $\bar D^* D^*\to\pi X$ and find that, in this case too, the $X\bar D^* D^*$ vertex is relevant. We also discuss the role of the charged components of $X$ in the determination of the production cross sections.

Polaritonic Feshbach resonance

A Feshbach resonance occurs when the energy of two interacting free particles comes to resonance with a molecular bound state. When approaching this resonance, dramatic changes in the interaction strength between the particles occur. Feshbach resonances have been an essential tool to control the atom interactions, which can even be switched from repulsive to attractive [1-4]. Thanks to Feshbach resonances many effects in ultracold atomic gases could be explored [5, 6]. Here we demonstrate a Feshbach resonance based on polariton spinor interactions that characterize the fundamental interaction process in polariton quantum systems. We show the clear enhancement of attractive interactions and the prompt change to repulsive interaction by tuning the energy of two polaritons with anti-parallel spins across the biexciton bound state energy. A mean field two-channel model quantitatively reproduces the experimental results. This observation paves the way for a new tool to tune the polariton interactions and to move forward into quantum correlated polariton physics.

Elliptic dichroism, ellipticity and the offset angle of high harmonics generated by arbitrary homonuclear diatomic molecules

The nth harmonic emission rate has contributions of the components of the T-matrix element in the direction of the laser-field polarization and in the direction perpendicular to it. Using both components of the T-matrix element we present a theoretical approach for calculation of the ellipticity and the offset angle of high harmonics. The molecular bound state is represented by HOMO or by HOMO-1. We show that high harmonics, generated by molecules oriented by an angle θL with respect to the major semiaxis of the laserfield polarization ellipse, are elliptically polarized even if the applied field is linearly polarized. Using examples of N2 and O2 molecules we show the existence of extrema and sudden changes of the harmonic ellipticity and the offset angle for particular molecular alignment. The interference between different contributions to the T-matrix element depends on the molecular symmetry. Presenting partial or total parameters of elliptic dichroism in the (θL, n) plane clear interference minima are observed. Therefore, the measurement of the elliptic dichroism may reveal information about the molecular structure and symmetry.

Strong-field approximation for above-threshold ionization of polyatomic molecules

We consider above-threshold ionization of polyatomic molecules by a strong laser field within the molecular strong-field approximation (MSFA). A polyatomic molecule is modeled by an $(N+1)$-particle system, which consists of $N$ heavy atomic (ionic) centers and an electron. After the separation of the center-of-mass coordinate, the dynamics of this system is reduced to the relative electronic and nuclear coordinates. Two forms of the MSFA, one with the field-free and the other with the field-dressed initial molecular bound state, are derived. For neutral polyatomic molecules the ionization amplitude takes a simple form which allows interpretation as a multiple-slit-type interference. This is illustrated by a numerical example for the ozone molecule.

Application of the dressed-bound-state molecular strong-field approximation to above-threshold ionization of heteronuclear molecules: NO vs. CO

We theoretically investigate high-order above-threshold ionization (HATI) of heteronuclear diatomic molecules applying the molecular strong-field approximation which includes dressing of the molecular bound state. We consider HATI of nitrogen monoxide molecules, which are characterized by the π symmetry of their highest occupied molecular orbital. We show that the HATI spectra of NO exhibit characteristic interference structures. We analyze the differences and similarities of the HATI spectra of NO molecules and the spectra of CO (σ symmetry) and O(2) (π(g) symmetry) molecules. The symmetry properties of the molecular HATI spectra governed by linearly and elliptically polarized fields are considered in detail. The yields of high-energy electrons, contributing to the plateau region of the photoelectron spectra, strongly depend on the employed ellipticity.

DKmolecule in the Bethe-Salpeter equation approach in the heavy quark limit

In the heavy quark limit, we establish the Bethe-Salpeter equation for the possible molecular state containing one heavy meson D and one light meson K. With the kernel induced by one-particle-exchange diagrams, we solve the Bethe-Salpeter equation numerically in the ladder and covariant instantaneous approximations and find that the DK bound state may exist. Assuming the observed state D*(s0)(2317)(+) is an S-wave DK molecular bound state we calculate the strong decay width of D*(s0)(2317)(+). Our prediction for the decay width Gamma(D*(s0)(2317)(+) -> D-s(+) pi(0)) is consistent with the previous investigations and the current experimental data.