Long-range States Research Articles

Adsorption of polyiodobenzene molecules on the Pt(111) surface using van der Waals density functional theory

Adsorption of aromatic molecules on surfaces is widely studied due to applications in molecular electronics. In this work, the adsorption of iodobenzene molecules on the Pt(111) surface has been studied using density functional theory. Iodobenzene molecules, with various numbers of iodine atoms, have two non-dissociative adsorption minima. One structure exhibits chemisorption between the ring and the surface (short-range) and the other structure exhibits chemisorption between the iodine ions and the surface (long-range). Both structures have a strong van der Waals interaction with the surface. In general, the adsorption energy increases as the number of iodine atoms increases. The dissociated structure of monoiodobenzene was investigated, and the dissociation barrier and the barrier between the short- and long-range states were compared.

Terahertz radiation induces non-thermal structural changes associated with Fröhlich condensation in a protein crystal.

Whether long-range quantum coherent states could exist in biological systems, and beyond low-temperature regimes where quantum physics is known to be applicable, has been the subject to debate for decades. It was proposed by Fröhlich that vibrational modes within protein molecules can order and condense into a lowest-frequency vibrational mode in a process similar to Bose-Einstein condensation, and thus that macroscopic coherence could potentially be observed in biological systems. Despite the prediction of these so-called Fröhlich condensates almost five decades ago, experimental evidence thereof has been lacking. Here, we present the first experimental observation of Fröhlich condensation in a protein structure. To that end, and to overcome the challenges associated with probing low-frequency molecular vibrations in proteins (which has hampered understanding of their role in proteins' function), we combined terahertz techniques with a highly sensitive X-ray crystallographic method to visualize low-frequency vibrational modes in the protein structure of hen-egg white lysozyme. We found that 0.4 THz electromagnetic radiation induces non-thermal changes in electron density. In particular, we observed a local increase of electron density in a long α-helix motif consistent with a subtle longitudinal compression of the helix. These observed electron density changes occur at a low absorption rate indicating that thermalization of terahertz photons happens on a micro- to milli-second time scale, which is much slower than the expected nanosecond time scale due to damping of delocalized low frequency vibrations. Our analyses show that the micro- to milli-second lifetime of the vibration can only be explained by Fröhlich condensation, a phenomenon predicted almost half a century ago, yet never experimentally confirmed.

Long-range states in excited ultracold 3He*–4He* dimers

Long-range bound states of the excited heteronuclear –He* system that dissociate to either (1s2s S1) + (1s2p Pj) or (1s2p Pj) + (1s2s S1), where , are investigated using both single-channel and multichannel calculations in order to analyse the effects of Coriolis and non-adiabatic couplings. The multichannel calculations predict two groups of resonances above the lowest asymptotic energy. One of these groups dissociates to an atomic pair with the 2p excitation on the fermionic atom and the other dissociates to two asymptotes which correspond to the 2p excitation on either atom. Many of these resonances could be identified with levels in the single-channel calculation although the differences in energies were large. The total parity was found to have a significant influence on the ability to make these identifications. No purely bound states were found, although several resonances with line widths smaller than 1 MHz were obtained.

Concurrent Effects of Delocalization and Internal Conversion Tune Charge Separation at Regioregular Polythiophene-Fullerene Heterojunctions.

Quantum-dynamical simulations are used to investigate the interplay of exciton delocalization and vibronically induced internal conversion processes in the elementary charge separation steps at regioregular donor-acceptor heterojunctions. Ultrafast internal conversion leads to efficient deexcitation within the excitonic and charge transfer manifolds, thus modifying the charge separation dynamics. We address a model donor-acceptor junction representative of regioregular P3HT-PCBM, using high-dimensional quantum dynamics simulations by multiconfigurational methods. While partial trapping into an interfacial charge separated state occurs, long-range charge-separated states are accessed as previously demonstrated in the work of Tamura and Burghardt [J. Am. Chem. Soc. 2013, 135, 16364]. For an H-aggregate type, stacked donor species, the initial bright state undergoes ultrafast internal conversion within the excitonic manifold, creating multiple charge transfer pathways before reaching the lowest-energy dark exciton, which is uncoupled from the charge transfer manifold. This process profoundly affects the charge separation mechanism and efficiency. For small energetic offsets between the interfacial excitonic and charge transfer states, a delocalized initial bright state proves less prone to electron-hole capture by the interfacial trap than a localized, vibronic wavepacket close to the interface. For both delocalized and localized initial states, a comparable yield of free carriers is obtained, which is found to be optimal for energetic offsets of the order of the Coulomb barrier to charge separation. Interfacial trapping is significantly reduced as the barrier height decreases with fullerene aggregation. Despite the high-dimensional nature of the system, charge separation is an ultrafast coherent quantum process exhibiting oscillatory features as observed in recent experiments.

A Simplified Method for Identification of the Vibrational Series of Long-Range States in Na2

We performed two-color photoassociative ionization experiments in cold sodium atoms in a dark MOT. We produce a sample where most of the atoms were in the ground hyperfine state F=1. Applying a laser with variable frequency, in the region of 0 to −32 GHz, we obtained a photoassociative spectra containing sequences of different long-range potentials. Using the scaling law for intermediate states, we identified the vibrational series of involved states, separating the sequences. In this way, we have identified the vibrational series for the $1_{g}, 0_{u}^{+}$ , and $0_{g}^{-}$ states contributions.

Interplay between short- and long-range entanglement in symmetry-protected phases

We study a variety of questions related to entanglement in symmetry-protected phases. These phases are analogous to topological insulators in that they are short-range entangled states with symmetry-protected edge or surface states. We show that the now standard bulk-edge correspondence relating the entanglement spectrum to the gapless edge spectrum holds for these phases as well. We further consider the question of coupling these models to gauge fields which we show gives an alternative way to construct different kinds of long-range entangled states without symmetry. We also argue that this procedure yields models with perturbatively stable edge or surface states at a variety of interface types. The non-onsite nature of the edge symmetry plays an important role in our considerations.

Direct optical generation of long-range charge-transfer states in organic photovoltaics.

Direct optical excitation of long-range charge-transfer (CT) states in organic photovoltaics is shown to be feasible, a fact that is ascribed to the very low but non-vanishing oscillator strength of each individual transition and the much higher density of states (DOS) as compared with their short-range counterparts. This finding provides a new framework to interpret the low-energy absorption spectra of photovoltaic devices and to correlate this property with the optoelectronic conversion process in working devices.

Optical Feshbach resonances through a molecular dark state: Efficient manipulation ofp-wave resonances in fermionicYb171atoms

In a recent experiment by Yamazaki {\it et al.} [Phys.Rev. A {\bf 87} 010704 (R) (2013) ], $p$-wave optical Feshbach resonance in fermionic $^{171}$Yb atoms using purely long-range molecular excited states has been demonstrated. We theoretically show that, if two purely long range excited states of $^{171}$Yb are coupled to the ground-state continuum of scattering states with two lasers, then it is possible to significantly suppress photoassociative atom loss by a dark resonance in the excited states. We present a general theoretical framework for creating a dark state in electronically excited molecular potential for the purpose of increasing the efficiency of an optical Feshbach resonance. This can be accomplished by properly adjusting the relative intensity, phase, polarizations and frequency detunings of two lasers. We present selective numerical results on atom loss spectra, $p$-wave elastic and inelastic scattering cross sections of $^{171}$Yb atoms to illustrate the effects of the molecular dark state on optical Feshbach resonance.

Photoexcitation of Light-Harvesting C–P–C60 Triads: A FLMO-TD-DFT Study

The recently proposed linear-scaling time-dependent density functional theory (TD-DFT) [ J. Chem. Comput. 2011 , 7 , 3643 ] is employed to capture more than 300 low-lying excited states for three light-harvesting C-P-C60 triads composed of β-carotenoid polyene (C), diaryl-based porphyrin (P), and pyrrole-fullerene (C60). The simulated optical absorption spectra are grossly in good agreement with experimental observations. To gain insights on the structure-property relations, both top-down and bottom-up analyses of the excited states are made in terms of the underlying fragment localized molecular orbitals (FLMO). A maximum occupation method is further proposed for finding excited-state solutions of self-consistent-field equations and is applied to long-range charge-transfer states that cannot be described by TD-DFT with pure density functionals.

Entanglement entropy for nonzero genus topologies

Over the last three decades entanglement entropy has been obtained for quantum fields propagating in genus zero topologies (Spheres). For scalar fields propagating in these topologies, it has been shown that the entanglement entropy scales as area. In the last few years non-trivial topologies are increasingly relevant for different areas. For instance, in describing quantum phases, it has been realized that long-range entangled states are described by topological order. If quantum entanglement can plausibly provide explanation for these, it then imperative to obtain entanglement entropy in these topologies. In this work, using two different methods, we explicitly show that the entanglement entropy scales as area of the genus-1 geometry.

Ordering phase relationships in ternary iron aluminides

One of the key issues in the development of iron aluminides is the thermodynamic modeling of alloying effects on the long-range and short-range order states of the underlying bcc phase, needed for the proper description of their effects upon phase equilibria and physical properties of multicomponent alloys. The present work describes results obtained by the present research group in the development of a thermodynamic database using the cluster variation method (CVM) in the irregular tetrahedron approximation, combined with ab initio results obtained from FP-LAPW electronic structure calculation in the GGA approximation, as embodied in the WIEN2k package. The ordering phase equilibria in isothermal sections of systems Fe–Al–Mo, Fe–Al–Nb and Fe–Al–Ti are compared. These equilibria, particularly in the technologically important iron-rich corner, are characterized by radically different behaviors, ranging from very large solubility of Ti in the L21/D03 and B2 phases, to a very small solubility of Mo. The behavior of Nb is somewhat intermediate between these two extremes, and shows a limited solubility in the B2 phase, which is, however, found in metastable equilibrium with a L21 phase. It can be shown that these different behaviors can be understood as a consequence of the different metastable equilibria in the binary Fe–Mo, Fe–Nb and Fe–Ti systems. The results are discussed in reference with experimental data on the stable and metastable ordering equilibria in these systems and are illustrated by their impact of aluminide physical properties, like diffusion and APB energies, with its implications for plastic deformation.

Relation between properties of long-range diatomic bound states

Long-range states of diatomic molecules have average values of internuclear separations $\ensuremath{\langle}R\ensuremath{\rangle}$ at least one order of magnitude larger than the equilibrium value of $R$. For example, the helium dimer ${{}^{4}\mathrm{He}}_{2}$ has a single bound state with $\ensuremath{\langle}R\ensuremath{\rangle}$ of about 50 \AA{}. We show that the properties of these states, such as $\ensuremath{\langle}R\ensuremath{\rangle}$, the dissociation energy, or the $s$-wave scattering length, can be related by simple, yet very accurate, formulas if a potential-energy curve is known. By examining a range of ab initio and empirical helium dimer potentials as well as scaling these potentials, we found that the formulas remain accurate, even if very approximate potentials were used. In addition to ${{}^{4}\mathrm{He}}_{2}$, we present results for ${{}^{9}\mathrm{Be}}_{2},\phantom{\rule{0.28em}{0ex}}{{}^{20}\mathrm{Ne}}_{2}$, and KRb.

Observation of ap-wave optical Feshbach resonance

We demonstrate a p$-wave optical Feshbach resonance (OFR) using purely long-range molecular states of a fermionic isotope of ytterbium ^{171}Yb, following the proposition made by K. Goyal et al. [Phys. Rev. A 82, 062704 (2010)]. The p-wave OFR is clearly observed as a modification of a photoassociation rate for atomic ensembles at about 5 micro-Kelvins. A scattering phase shift variation of \delta \eta=0.022 rad is observed with an atom loss rate coefficient K=28.0*10^{-12} cm^3/s.

Initial Molecular Photocurrent: Nanostructure and Motion of Weakly Bound Charge-Separated State in Organic Photovoltaic Interface

To elucidate mechanism of the efficient photocarrier generation by the photoactive bulkheterojunction layers of the organic photovoltaic (OPV) devices, we have employed the time-resolved electron paramagnetic resonance method on solid blends composed of [6,6]-C61-butyric acid methyl ester (PCBM) and of poly(3-hexylthiophene-2,5-diyl) (P3HT) with different regioregularities. The photoinduced charge-separated (CS) states have been detected at the boundary regions between the P3HT and PCBM domains at T = 77 K. We have characterized molecular geometries, electronic couplings, and molecular motions of the long-range CS states. From the CS structure, it is indicated that the pentagonal or hexagonal aromatic rings of the buckyball in PCBM directly face the aromatic plane of the π-stacked P3HT surfaces. It has been concluded that the distant CS states are produced via fast hole-delocalization process from the contact charge-transfer (CT) states. Such hole dynamics is explained by a coupling of the hole to librations of chains in the conjugated polymer. It has been concluded that both the enthalpy stabilization and the enhancement of the entropy occur through the orbital delocalization by the electron–phonon coupling, overcoming the initial CT binding to generate the molecular photocurrent.

Preface

IUPAC’s vision statement declares that the Union advances the worldwide role of chemistry for the benefit of Mankind. And one of its long-range goals states “IUPAC will utilize its global perspective and network to contribute to the enhancement of chemistry education, the career development of young chemical scientists, and the public appreciation of chemistry”. In pursuit of this spirit, the Union established in 2000 the IUPAC Prize for Young Chemists and has been honoring since then outstanding young research chemists at the beginning of their careers by making annual awards. The prizes are given for the most outstanding Ph.D. theses in the area of the chemical sciences, as described in 1000-word essays.As immediate Past President of IUPAC, I was honored to chair the prize selection committee of eminent chemists, who enjoyed reading essays of 41 applicants from 22 countries. After critical evaluation of the originality and excellence of the essays and research results, the committee decided unanimously to award 2012 Prizes for the following six essays:- “Study of the factors affecting the selectivity of catalytic ethylene oligomerization”, Khalid Albahily, University of Ottawa, Ottawa, Canada (following earlier studies at King Saud University, Saudi Arabia and Texas A&M University, College Station, TX, USA)- “Nanowire nanoelectronics: Building interfaces with tissue and cells at the natural scale of biology”, Tzahi Cohen-Karni, Harvard University, Cambridge, MA, USA (following earlier studies at Technion Israel Institute of Technology and Weizmann Institute of Science, Israel)- “Synthetic investigations featuring boron-rich and multidentate chalcoether-containing ligands”, Alexander Spokoyny, Northwestern University, Chicago, IL, USA (following earlier studies at University of California, Los Angeles, CA, USA)- “Quantification of virtual chemical properties: Strain, hyperconjugation, conjugation, and aromaticity”, Judy I-Chia Wu, University of Georgia, Athens, GA, USA (following earlier studies at Tung-Hai University, Taiwan)- “New materials for intermediate-temperature solid oxide fuel cells to be powered by carbon- and sulfur-containing fuels”, Lei Yang, Georgia Institute of Technology, Atlanta, GA, USA (following earlier studies at Beihang University and Tsinghua University, China)- “Transition metal catalysis: Activation of CO2, C–H, and C–O bonds en route to carboxylic acids, biaryls, and N-containing heterocycles”, Charles Yeung, University of Toronto, Toronto, Canada (following earlier studies at University of British Columbia, Vancouver, Canada)All the awardees were invited to present posters on their research at the 44th IUPAC World Chemistry Congress, Istanbul, Turkey, 11–16 August 2012. Upon IUPAC’s invitation, 4 of the 6 winners offered review papers on their research topics for consideration as publications in this issue of Pure and Applied Chemistry.Finally, it is an honor and a pleasure to congratulate each of the winners and their supervisors for winning the 2012 IUPAC Prize for Young Chemists. It is hoped that each of them will continue to contribute to a bright future for chemical sciences and technologies and to take active roles in IUPAC bodies in the future.Nicole MoreauIUPAC Immediate Past President and Chair of the IUPAC Prize Selection Committee

Electronic energy transfer between long-range resonance states of 3-mercaptopropionic acid capped CdTe quantum dots in aqueous media

We demonstrate electronic energy transfer between resonance states of 2 and 2.8 nm CdTe quantum dots in aqueous media using steady-state photoluminescence spectroscopy without using any external linker molecule. With increasing concentration of larger dots, there is subsequent quenching of luminescence in smaller dots accompanied by the enhancement of luminescence in larger dots. Our experimental evidence suggests that there is long-range resonance energy transfer among electronic excitations, specifically from the electronically confined states of the smaller dots to the higher excited states of the larger dots.

Preface

<div>IUPAC’s vision statement declares that the Union advances the worldwide role of chemistry for the benefit of Mankind. And one of its long-range goals states “IUPAC will utilize its global perspective and network to contribute to the enhancement of chemistry education, the career development of young chemical scientists, and the public appreciation of chemistry”. In pursuit of this spirit, the Union established in 2000 the IUPAC Prize for Young Chemists and has been honoring since then outstanding young research chemists at the beginning of their careers by making annual awards.<br /><br />The prizes are given for the most outstanding Ph.D. theses in the area of the chemical sciences, as described in 1000-word essays. For details, please refer to <http://www.iupac.org/news/prize.html> (IUPAC Prizes for Young Chemists). IUPAC awards up to five prizes annually, each comprising USD 1000 and travel expenses to the next IUPAC Congress.<br /><br />As immediate Past President of IUPAC, I was honored to chair the prize selection committee of eminent chemists, who enjoyed reading essays of 47 applicants from 19 countries. The committee was extremely pleased to note the increase in the number of applicants to 47 from 29 last year. This increase is in excellent accord with IUPAC’s worldwide celebration of the International Year of Chemistry throughout this year. After critical evaluation of the originality and excellence of the essays and research results, the committee decided unanimously to award 2011 Prizes to the following six chemists:<br /><br /><b>Rubén D. Costa</b>, University of Valencia, Valencia, Spain: “Theoretical and experimental study of light-emitting electrochemical cells based on ionic transition-metal complexes: From the molecule to the device”<br /><br /><b>William Donald</b>, University of California, Berkeley, CA, USA: “Ion nanocalorimetry: Measuring absolute reduction potentials and investigating effects of water on electron solvation and ion fluorescence”<br /><br /><b>Matthew Macauley</b>, Simon Fraser University, Burnaby, BC, Canada: “Insight into O-GlcNAc protein modification using chemical and biochemical tools”<br /><br /><b>Bozhi Tian</b>, Harvard University, Cambridge, MA, USA: “Design, synthesis, and characterization of novel nanowire structures for photovoltaics and intracellular probes”<br /><br /><b>Sheng Xu</b>, Georgia Institute of Technology, Atlanta, GA, USA: “Oxide nanowire arrays for energy sciences”<br /><br /><b>Chengqi Yi</b>, University of Chicago, Chicago, IL, USA: “Probing the AlkB family DNA/RNA repair enzymes with a chemical disulphide cross-linking approach”<br /><br />All the awardees were invited to present posters on their research at the 43rd IUPAC World Chemistry Congress, San Juan, Puerto Rico, 30 July-6 August 2011. Upon IUPAC’s invitation, five of the six winners offered review papers on their research topics for consideration as publications in <i>Pure and Applied Chemistry (PAC)</i>. And the five refereed articles appear in this issue of <i>PAC</i>.<br /><br />Finally, it is an honor and a pleasure to congratulate each of the winners and their supervisors for winning the 2011 IUPAC Prize for Young Chemists. It is hoped that each of them will continue to contribute to a bright future for chemical sciences and technologies and to take active roles in IUPAC bodies in the future.<br /><br /><b>Jung-Il Jin</b><br />IUPAC Immediate Past President and Chair of the IUPAC Prize Selection Committee<br /><br /></div>

Theoretical studies of photoassociation in ultracold metastable helium

Line shifts and line shapes for photoassociation of spin-polarised metastable helium to long-range vibrational states in the J = 1,0+u potential dissociating to the 2s3S1 + 2p 3P0 limit are studied using a nonperturbative multichannel calculation valid for arbitrary laser intensities. Asymptotically-free dressed states of the laser plus matter system are used to obtain the S-matrix elements required to generate the photoassociation profiles. Issues associated with the very shallow nature of the potentials that support the excited states are investigated.

Theoretical investigation of the Ωg,u(+/−) states of K2 dissociating adiabatically up to K(4p P23/2)+K(4p P23/2)

A theoretical investigation of the electronic structure of the K(2) molecule, including spin-orbit effects, has been performed. Potential energies have been calculated over a large range of R up to 75a(0) for the 88 Omega(g,u)(+/-) states dissociating adiabatically into the limits up to K(4p (2)P(3/2))+K(4p (2)P(3/2)). Equilibrium distances, transition energies, harmonic frequencies, as well as depths for wells and heights for barriers are reported for all of the bound Omega(g,u)(+/-) states. Present ab initio calculations are shown to be able to reproduce quite accurately the small structures (wells and barrier) displayed at very long-range (R>50a(0)) by the (2,3)1(u) and (2)0(g)(-) purely long-range states. As the present data could help experimentalists, we make available extensive tables of energy values versus internuclear distances in our database at the web address http://www-lasim.univ-lyon1.fr/spip.php?rubrique99.

Photoassociative molecular spectroscopy for atomic radiative lifetimes

When the atoms of a dimer remain most of the time very far apart, in so-called long-range molecular states, their mutual interaction is ruled by plain atomic properties. The high-resolution spectroscopic study of some molecular excited states populated by photoassociation of cold atoms (photoassociative spectroscopy) gives a good illustration of this property. It provides accurate determinations of atomic radiative lifetimes, which are known to be sensitive tests for atomic calculations. A number of such analyses have been performed up to now, for all stable alkali atoms and for some other atomic species (Ca, Sr, Yb). A systematic review of these determinations is attempted here, with special attention paid to accuracy issues.