Molecular polaritons, hybrid light-matter states formed from the strong coupling of molecular transitions and discrete photonic modes, are a compelling platform for optical control of chemical reactivity. Despite the origins of the field of polaritonics in atomic gases, strong coupling of molecular gases remains underexplored. The pristine, solvent-free gas-phase environment may prove ideal for gaining mechanistic understanding of molecular behavior under strong light-matter coupling. In this work, we achieve electronic strong coupling of the B-X, $ν_1$ = 0$\rightarrow$32, J = 53$\rightarrow$52 and B-X, $ν_1$ = 0$\rightarrow$34, J = 103$\rightarrow$102 rovibronic transitions of gas-phase iodine (I$_2$) lying near 532.2 nm. We access a range of coupling strengths and detuning conditions with fine control over molecular number density and cavity length stabilization. This effort represents the first demonstration of electronic polaritons in a molecular gas and opens a new platform for polariton photochemistry and photophysics.
The lifetime of the $E^3Π_g(v=3)$ state of molecular iodine was measured in the gas phase at room temperature. The $E^3Π_g$ state was selectively populated by two sequential nanosecond pulse laser excitation. Resolved molecular fluorescence for the $B^3Π_u^+\leftarrow E^3Π_g$ was analyzed and the lifetime of the $E(v=3)$ state, measured using a time-correlated single photon counting technique, is to be $τ=21 (2)$ ns.
Metallization and dissociation are key transformations in diatomic molecules at high densities particularly significant for modeling giant planets. Using X-ray absorption spectroscopy and atomistic modeling, we demonstrate that in halogens, the formation of a \textit{connected} molecular structure takes place at pressures well below metallization. Here we show that the iodine diatomic molecule first elongates of $\sim$0.007 Å~up to a critical pressure of $P_c$ $\backsim$7~GPa developing bonds between molecules. Then its length continuously decreases with pressure up to 15-20~GPa. Universal tre…
Despite the highly porous nature with significantly large surface area, metal organic frameworks (MOFs) can be hardly used in electronic, and optoelectronic devices due to their extremely poor electrical conductivity. Therefore, the study of MOF thin films that require electron transport or conductivity in combination with the everlasting porosity is highly desirable. In the present work, thin films of Co3(NDC)3DMF4 MOFs with improved electronic conductivity are synthesized using layer-by-layer and doctor blade coating techniques followed by iodine doping. The as-prepared and doped films are c…
Imaging transient molecular configurations in UV-excited diiodomethane
Kansas State University（堪萨斯州立大学）；SLAC National Accelerator Laboratory（斯坦福直线加速器中心）；University of Science and Technology of China（中国科学技术大学）；Southern University of Science and Technology（南方科技大学）
We show that time-resolved x-ray scattering from molecules prepared in a superposition of electronic states moving through an avoided crossing has new features not found in diffraction from the corresponding classical mixed state. Photoabsorption in molecular iodine at 520 nm produces a superposition of two dipole-allowed nearly degenerate electronic states, which interact due to non-adiabatic coupling. We show experimental evidence that the mixing of the nuclear wavepackets from the two electronic states at the avoided crossing leads to ultrafast changes in the angular composition of the scat…
Few examples of the exploitation of molecular magnetic properties in molecular electronics are known to date. Here we propose the realization of Self assembled monolayers (SAM) of a particular stable organic radical. This radical is meant to be used as a standard molecule on which to prove the validity of a single spin reading procedure known as ESR-STM. We also discuss a range of possible applications, further than ESR-STM, of magnetic monolayers of simple purely organic magnetic molecule.
Molecular polaritons have become an emerging platform for remotely controlling molecular properties through strong light-matter interactions. Herein, a semiclassical approach is developed for describing molecular polaritons by self-consistently propagating the real-time dynamics of classical cavity modes and a quantum molecular subsystem described by the nuclear-electronic orbital (NEO) method, where electrons and specified nuclei are treated quantum mechanically on the same level. This semiclassical real-time NEO approach provides a unified description of electronic and vibrational strong cou…
Quantum beats in nonlinear spectroscopy of molecular aggregates are often attributed to electronic phenomena of excitonic systems, while nuclear degrees of freedom are commonly included into models as overdamped oscillations of bath constituents responsible for dephasing. However, molecular systems are coupled to various high-frequency molecular vibrations, which can cause the spectral beats hardly distinguishable from those created by purely electronic coherences. Models containing damped, undamped and overdamped vibrational modes coupled to an electronic molecular transition are discussed in…
We show that the origin of electronic transitions of molecular many-body systems can be revealed by a quantified natural transition orbitals (QNTO) analysis and the electronic excitations of the total system can be mapped onto a standard orbitals set of a reference system. We further illustrate QNTO on molecular systems by studying the origin of electronic transitions of DNA moiety, thymine and thymidine. This QNTO analysis also allows us to assess the performance of various functionals used in time-dependent density functional response theory.
Representation of molecular vibrational degrees of freedom by independent harmonic oscillators, when describing electronic spectra or electronic excitation energy transport, raises unfavourable effects as vibrational energy relaxation becomes inaccessible. A standard theoretical description is extended in this paper by including both electronic-phonon and vibrational-phonon couplings. Using this approach we have simulated a model pigment-protein system and have shown that intermode coupling leads to the quenching of pigment vibrational modes, and to the redistribution of fluctuation spectral d…
Coherent dynamics of coupled molecules are effectively characterized by the two-dimensional (2D) electronic coherent spectroscopy. Depending on the coupling between electronic and vibrational states, oscillating signals of purely electronic, purely vibrational or mixed origin can be observed. Even in the "mixed" molecular systems two types of coherent beats having either electronic or vibrational character can be distinguished by analyzing oscillation Fourier maps, constructed from time-resolved 2D spectra. The amplitude of the beatings with the electronic character is heavily affected by the …
An approximate relativistic two-component Hamiltonian for use in molecular electronic structure calculations is derived in the form of a sum of fixed atom-centered kinetic and spin-orbit operators added to the non-relativistic Hamiltonian. Starting from the well-known zeroth-order regular approximation, further steps are taken to get rid of its nonlinearity in the potential, ending up with a simple formulation with easily computable integrals that can seamlessly work with any traditional electronic structure method. Molecular tests show a good accuracy of this approximation.
We introduce two different approaches to represent the second-quantized electronic Hamiltonian in a sum-of-products form. These procedures aim at mitigating the quartic scaling of the number of terms in the Hamiltonian with respect to the number of spin orbitals, and thus enable applications to larger molecular systems. Here we describe the application of these approaches within the multi-configuration time-dependent Hartree framework. This approach is applied to the calculation of eigen energies of LiH and electronic ionization spectrum of H2O.
The electronic structures of the manifold of potential energy surfaces generated in the lower energy range by the interaction of the MgH$^+$(X$^1Σ^+$) cationic molecule with Rb($^2$S), neutral atom are obtained over a broad range of Jacobi coordinates from strongly correlated \emph{ab initio} calculations which use a Multireference (MR) wavefunction within a Complete Active Space (CAS) approach. The relative features of the lowest five surfaces are analyzed in terms of possible collisional outcomes when employed to model the ultracold dynamics of ionic molecular partners.
Atomic effective one-electron potentials in a compact analytic form in terms of a few Gaussian charge distributions are developed, for Hydrogen through Nobelium, for starting molecular electronic structure calculations by a simple diagonalization. For each element, all terms but one are optimized in an isolated-atom Hartree--Fock calculation, and the last one is parametrized on a set of molecules. This one-parameter-per-atom model gives a good starting guess for typical molecules and may be of interest even on its own.
A kink-based path integral method, previously applied to atomic systems, is modified and used to study molecular systems. The method allows the simultaneous evolution of atomic and electronic degrees of freedom. Results for CH$_4 $, NH$_3 $, and H$_2 $O demonstrate this method to be accurate for both geometries and energies. Comparison with DFT and MP2 level calculations show the path integral approach to produce energies in close agreement with MP2 energies and geometries in close agreement with both DFT and MP2 results.
The two-dimensional spectroscopy has recently revealed oscillatory behavior of excitation dynamics in molecular systems. However, in the majority of cases it is strongly debated if excitonic or vibrational wavepackets, or evidences of quantum transport have been observed. In this letter, the method for distinguishing between vibrational and excitonic wavepacket motion is presented, based on the phase and amplitude relationships of oscillations of distinct peaks, which has been revealed using fundamental analysis of two-dimensional spectrum of two representative systems.
We report experimental results on the diffractive imaging of three-dimensionally aligned 2,5-diiodothiophene molecules. The molecules were aligned by chirped near-infrared laser pulses, and their structure was probed at a photon energy of 9.5 keV ($λ\approx130 \text{pm}$) provided by the Linac Coherent Light Source. Diffracted photons were recorded on the CSPAD detector and a two-dimensional diffraction pattern of the equilibrium structure of 2,5-diiodothiophene was recorded. The retrieved distance between the two iodine atoms agrees with the quantum-chemically calculated molecular structure t…
We investigate the electronic stress tensor of the hydrogen molecular ion for the ground state using the exact wave function and wave functions approximated by gaussian function basis set expansion. The spatial distribution of the largest eigenvalue, corresponding eigenvectors, tension and kinetic energy density are compared. We find that the cc-pV6Z basis set gives the spindle structure very close to the one calculated from the exact wave function. Similarly, energy density at the Lagrange point is very well approximated by the cc-pV5Z or cc-pV6Z basis sets.
Electronic current flowing in a molecular electronic junction dissipates significant amounts of energy to vibrational degrees of freedom, straining and rupturing chemical bonds and often quickly destroying the integrity of the molecular device. The infamous mechanical instability of molecular electronic junctions critically limits performance, lifespan, and raises questions as to the technological viability of single-molecule electronics. Here we propose a practical scheme for cooling the molecular vibrational temperature via application of an AC voltage over a large, static operational DC vol…
We analyze the effect of an external electric field on the electronic structure of molecules which have been recently studied as molecular wires or diodes. We use a self-consistent tight binding technique which provides results in good agreement with ab initio calculations and which may be applied to a large number of molecules. The voltage dependence of the molecular levels is mainly linear with slopes intimately related to the electronic structure of the molecules. We emphasize that the response to the applied voltage is an important feature which governs the behavior of a molecular device.
The coupling of electronic and vibrational motion is studied by two canonical transformations namely normal coordinate transformation and momentum transformation on molecular Hamiltonian. It is shown that by these transformations we can pass from crude approximation to adiabatic approximation and then to non-adiabatic (diabatic) Hamiltonian. This leads to renormalized fermions and renormalized diabatic phonons. Simple calculations on $H_{2}$, $HD$, and $D_{2}$ systems are performed and compared with previous approaches. Problem of electronic quasi-degeneracy is discussed.
We present a perturbation approach rooted in time-dependent density-functional theory to calculate electron hole (eh)-pair excitation spectra during the non-adiabatic vibrational damping of adsorbates on metal surfaces. Our analysis for the benchmark systems CO on Cu(100) and Pt(111) elucidates the surprisingly strong influence of rather short electronic coherence times. We demonstrate how in the limit of short electronic coherence times, as implicitly assumed in prevalent quantum nuclear theories for the vibrational lifetimes as well as electronic friction, band structure effects are washed o…
We perform highly accurate calculations of the leading order QED correction to the ground electronic state of molecular hydrogen. Numerical results are obtained for a grid of the internuclear distances $R=0-10$ au with the relative precision of about $10^{-8}$. The major numerical uncertainty of previous QED results [K. Piszczatowski et al., JCTC $\textbf{5}$, 3039 (2009)] has been eliminated. Nevertheless, the discrepancy with measurements in HD at the level of 1.9 $σ$ persists.
We report on the largest dataset of optimized molecular geometries and electronic properties calculated by the PM6 method for 92.9% of the 91.2 million molecules cataloged in PubChem Compounds retrieved on Aug. 29, 2016. In addition to neutral states, we also calculated those for cationic, anionic, and spin flipped electronic states of 56.2%, 49.7%, and 41.3% of the molecules, respectively. Thus, the grand total calculated is 221 million molecules. The dataset is available at http://pubchemqc.riken.jp/pm6_dataset.html under the Creative Commons Attribution 4.0 International license.
We present the implementation of an electronic-structure approach dedicated to ionization dynamics of molecules interacting with x-ray free-electron laser (XFEL) pulses. In our scheme, molecular orbitals for molecular core-hole states are represented by linear combination of numerical atomic orbitals that are solutions of corresponding atomic core-hole states. We demonstrate that our scheme efficiently calculates all possible multiple-hole configurations of molecules formed during XFEL pulses. The present method is suitable to investigate x-ray multiphoton multiple ionization dynamics and acco…
Molecular ions formed in cold hybrid ion-atom experiments may find interesting applications ranging from precision measurements to controlled chemical reactions. Here, we investigate electronic structure of the Sr$_2^+$ molecular ion, which may be produced by photoassociation of laser-cooled Sr$^+$ ions immersed into an ultracold gas of Sr atoms or by ionization of ultracold Sr$_2$ molecules. Using \textit{ab initio} electronic structure methods, such as the coupled cluster and configuration interaction ones with small-core relativistic energy-consistent pseudopotentials and large Gaussian bas…
In this study, we explore the use of molecules and molecular electronics for quantum computing. We construct one-qubit gates using one-electron scattering in molecules, and two-qubit controlled-phase gates using electron-electron scattering along metallic leads. Furthermore, we propose a class of circuit implementations, and show initial applications of the framework by illustrating one-qubit gates using the molecular electronic structure of molecular hydrogen as a baseline model.
Quantum descriptions of many complex systems are formulated most naturally in bases of states that are not mutually orthogonal. We introduce a general and powerful yet simple approach that facilitates solving such models exactly by embedding the non-orthogonal states in a new Hilbert space in which they are by definition mutually orthogonal. This novel approach is applied to electronic transport in molecular quantum wires and is used to predict conductance antiresonances of a new type that arise solely out of the non-orthogonality of the local orbitals on different sites of the wire.
The study of the high pressure phase diagram of hydrogen has continued with renewed effort for about one century as it remains a fundamental challenge for experimental and theoretical techniques. Here we employ an efficient molecular dynamics based on the quantum Monte Carlo method, which can describe accurately the electronic correlation and treat a large number of hydrogen atoms, allowing a realistic and reliable prediction of thermodynamic roperties. We find that the molecular liquid phase is unexpectedly stable and the transition towards a fully atomic liquid phase occurs at much higher pr…
Feynman path-integral deep potential molecular dynamics (PI-DPMD) calculations have been employed to study both light (H$_2$O) and heavy water (D$_2$O) within the isothermal-isobaric ensemble. In particular, the deep neural network is trained based on ab initio data obtained from the strongly constrained and appropriately normed (SCAN) exchange-correlation functional. Because of the lighter mass of hydrogen than deuteron, the properties of light water is more influenced by nuclear quantum effect than those of heavy water. Clear isotope effects are observed and analyzed in terms of hydrogen-bon…
The translational motion of molecular ions can be effectively cooled sympathetically to translational temperatures below 100 mK in ion traps through Coulomb interactions with laser-cooled atomic ions. The ro-vibrational degrees of freedom, however, are expected to be largely unaffected during translational cooling. We have previously proposed schemes for cooling of the internal degrees of freedom of such translationally cold but internally hot heteronuclear diatomic ions in the simplest case of ^1-Sigma electronic ground state molecules. Here we present a significant simplification of these sc…
MOL-Mamba: Enhancing Molecular Representation with Structural & Electronic Insights
School of Computer Science and Information Engineering, Hefei University of Technology（合肥工业大学计算机与信息工程学院）；Institute of Artificial Intelligence, Hefei Comprehensive National Science Center（合肥综合性国家科学中心人工智能研究院）；Anhui University（安徽大学）；University of Science and Technology of China（中国科学技术大学）
We recalculate the leading relativistic corrections for the ground electronic state of the hydrogen molecule using variational method with explicitly correlated functions which satisfy the interelectronic cusp condition. The new computational approach allowed for the control of the numerical precision which reached about 8 significant digits. More importantly, the updated theoretical energies became discrepant with the known experimental values and we conclude that the yet unknown relativistic recoil corrections might be larger than previously anticipated.
Experiments with cold ion-atom mixtures have recently opened the way for the production and application of ultracold molecular ions. Here, in a comparative study, we theoretically investigate ground and several excited electronic states and prospects for the formation of molecular ions composed of a calcium ion and an alkali-metal atom: CaAlk$^{+}$ (Alk=Li, Na, K, Rb, Cs). We use a quantum chemistry approach based on non-empirical pseudopotential, operatorial core-valence correlation, large Gaussian basis sets, and full configuration interaction method for valence electrons. Adiabatic potentia…
We have studied transition metal clusters from a quantum information theory perspective using the density-matrix renormalization group (DMRG) method. We demonstrate the competition between entanglement and interaction localization. We also discuss the application of the configuration interaction based dynamically extended active space procedure which significantly reduces the effective system size and accelerates the speed of convergence for complicated molecular electronic structures to a great extent. Our results indicate the importance of taking entanglement among molecular orbitals into ac…
