Electronic Population Research Articles

Vibronic Effects in the Ultrafast Interfacial Electron Transfer of Perylene-Sensitized TiO2 Surfaces

We combine ultrafast transient absorption (TA) spectroscopy and nonadiabatic quantum dynamics simulations to describe the real-time unfold of vibronic effects on the photoabsorption of TiO2 anatase sensitized with the (perylen-9-yl)carboxylate dye (Pe-COOH/TiO2). The excited state is mapped in time and frequency by ultrafast broadband spectroscopy while atomistic quantum dynamics is used to simulate the self-consistent vibronic effects. The TA map shows the lifetime of the electronic population generated in the S1 state of the dye and the rise of the absorption D0–D1 of the cation. The theoretical analysis reveals that the electron transfer from perylene into TiO2 is complete within 20 fs, in agreement with the 12 fs experimental measurement. Because of the structural relaxation produced by the photoinduced electron transfer, the optical gap decreases by 390 meV, in agreement with the D0–D1 transition band. Furthermore, the reorganization energy estimated to be around 220 meV is mostly due to the energy s...

Assessing the performance of trajectory surface hopping methods: Ultrafast internal conversion in pyrazine.

Trajectory surface hopping (TSH) methods have been widely used to study photoinduced nonadiabatic processes. In the present study, nonadiabatic dynamics simulations with the widely used Tully's fewest switches surface hopping (FSSH) algorithm and a Landau-Zener-type TSH (LZSH) algorithm have been performed for the internal conversion dynamics of pyrazine. The accuracy of the two TSH algorithms has been critically evaluated by a direct comparison with exact quantum dynamics calculations for a model of pyrazine. The model comprises the three lowest excited electronic states (B3u(nπ*), A1u(nπ*), and B2u(ππ*)) and the nine most relevant vibrational degrees of freedom. Considering photoexcitation to the diabatic B2u(ππ*) state, we examined the time-dependent diabatic and adiabatic electronic population dynamics. It is found that the diabatic populations obtained with both TSH methods are in good agreement with the exact quantum results. Fast population oscillations between the B3u(nπ*) and A1u(nπ*) states, which reflect nonadiabatic electronic transitions driven by coherent dynamics in the normal mode Q8a, are qualitatively reproduced by both TSH methods. In addition to the model study, the TSH methods have been interfaced with the second-order algebraic diagrammatic construction ab initio electronic-structure method to perform full-dimensional on-the-fly nonadiabatic dynamics simulations for pyrazine. It is found that the electronic population dynamics obtained with the LZSH method is in excellent agreement with that obtained by the FSSH method using a local diabatization algorithm. Moreover, the electronic populations of the full-dimensional on-the-fly calculations are in excellent agreement with the populations of the three-state nine-mode model, which confirms that the internal conversion dynamics of pyrazine is accurately represented by this reduced-dimensional model on the time scale under consideration (200 fs). The original FSSH method, in which the electronic wave function is propagated in the adiabatic representation, yields less accurate results. The oscillations in the populations of the diabatic B3u(nπ*) and A1u(nπ*) states driven by the mode Q8a are also observed in the full-dimensional dynamics simulations.

Fluorescence-Encoded Infrared Spectroscopy: Ultrafast Vibrational Spectroscopy on Small Ensembles of Molecules in Solution.

Fluorescence-encoded infrared (FEIR) spectroscopy is an ultrafast technique that uses a visible pulse to up-convert information about IR-driven vibrations into a fluorescent electronic population. Here we present an updated experimental approach to FEIR that achieves high sensitivity through confocal microscopy, high repetition rate excitation, and single-photon counting. We demonstrate the sensitivity of our experiment by measuring ultrafast vibrational transients and Fourier transform spectra of increasingly dilute solutions of a coumarin dye. We collect high-quality data at 40 μM (∼2 orders of magnitude below the limit for conventional IR) and make measurements down to the 10-100 nM range (∼5 orders of magnitude) before background signals become overwhelming. At 10 nM we measure the average number of molecules in the focal volume to be ∼20 using fluorescence correlation spectroscopy. This level of sensitivity opens up the possibility of performing fluctuation correlation vibrational spectroscopy or-with further improvement-single-molecule measurements.

Computational Study on Possible High Potential Ilmenite Type Na1TMO3 (TM=3d, 4d Transition Metals) Cathodes Based on Oxygen Redox Reaction

Na is a probable alternative for Li in rechargeable batteries due to its lower cost and higher abundance. Na, however, has a larger ionic radius and smaller ionisation potential compared to Li. Given these shortcomings, to design a Na ion based cathode material comparable in performance to Li, all mechanisms that may increase the capacity and voltage beyond that of the current limits should be carefully fine-tuned [1]. Here, through comprehensive density functional calculations, we screened the full range of ternary hexagonal layered compounds with ilmenite structure (space group 158) that consist of Na, O and 4d or 3d transition elements (TM) in search for candidates with a possibly higher operating voltage. The investigated TMs were V, Cr, Mn, Fe, Co, Ni, Nb, Mo, Tc, Ru, Rh, Pd and Ag. In the calculations, we treated the exchange-correlation interaction of the 3d TM containing compounds with hybrid HSE03 functional to account for the strong correlation effects. For 4d TM cases, on the other hand, we found that the GGA+U formalism sufficed for describing the band structure accurately. We, furthermore, found that a Ueff value of 2 eV could particularly reproduce the electrochemical potential of Na extraction in NaxRuO3 compound [2], which we then utilised for the rest of 4d TM containing compounds. Figures 1(a) and (b) show the structure of the sodiated compound Na1TMO3 (R-3) and the desodiated compound Na0.5TMO3 (P-31m) respectively. In the ilmenite type Na1TMO3, due to the R-3 symmetry, O ions are coordinated by two TM and two Na ions and two vacant sites. In this case, O under-coordination elevates the unhybridised or orphaned portion of O 2p states closer to the Fermi level. High O electronic population near the Fermi level facilitates greater O participation in redox over a wide range of Na concentrations. Since the potential associated with O redox is higher than that of TM redox, this mechanism also offers a new opportunity to achieve high voltage cathodes. Accordingly, our most notable prediction was Na1VO3 that is likely to have a potential of 5.91 V and is thermodynamically stable with respect to major competing NaxVyOz compounds promising excellent cyclability. Interestingly, the redox mechanism in Na1VO3 is entirely borne on O centres as V has a d0 configuration. Similarly, Na1NbO3 was also found to be another suitable and economic candidate for high voltage and high capacity Na ion batteries with a voltage of 4.94 V which is entirely O borne [2]. We also found that Na1FeO3, Na1MnO3 and Na1RuO3 have a desirable potential of 5.18 V and 4.53 V and 3.72 V respectively. Finally, according to our calculations, large O–O distances in the R-3 structure during cycling likely inhibit O–O bonding and subsequent O2 evolution which are otherwise detrimental to the battery application. Fig. 1. (a) and (b) are the schematic representation of the sodiated ilmenite type Na1TMO3 (R-3 symmetry) and the desodiated Na0.5TMO3 (P-31m symmetry), respectively. Reference s : [1] B. M. de Boisse, M. Okubo, A. Yamada et al., Nat. Commun., 7, 11397 (2016). [2] H. M. N. Assadi, M. Okubo, A. Yamada, Y. Tateyama, J. Mater. Chem. A 6, 3747-3753 (2018). Figure 1

Steady states of interacting Floquet insulators

Floquet engineering offers tantalizing opportunities for controlling the dynamics of quantum many body systems and realizing new nonequilibrium phases of matter. However, this approach faces a major challenge: generic interacting Floquet systems absorb energy from the drive, leading to uncontrolled heating which washes away the sought after behavior. How to achieve and control a non-trivial nonequilibrium steady state is therefore of crucial importance. In this work, we study the dynamics of an interacting one-dimensional periodically-driven electronic system coupled to a phonon heat bath. Using the Floquet-Boltzmann equation (FBE) we show that the electronic populations of the Floquet eigenstates can be controlled by the dissipation. We find the regime in which the steady state features an insulatorlike filling of the Floquet bands, with a low density of additional excitations. Furthermore, we develop a simple rate equation model for the steady state excitation density that captures the behavior obtained from the numerical solution of the FBE over a wide range of parameters.

Fully quantal treatment of nonadiabatic molecular photodynamics: General considerations and application to the benzene cation

The merits and drawbacks of a mixed quantum-classical description of nuclear motion on coupled potential energy surfaces are discussed and compared with a fully quantal treatment. For the latter a particular approach is highlighted in which an efficient wavepacket propagation scheme, the Multiconfiguration Time-Dependent Hartree (MCTDH) method, is combined with a versatile modeling of the Hamiltonian for interacting potential energy surfaces, the linear vibronic coupling (LVC) model. As an illustrative example this fully quantal treatment is applied to the benzene radical cation, where nuclear motion on five multiply intersecting potential energy surfaces with up to eleven nuclear degrees of freedom has been studied. The results for the electronic population dynamics allow to understand recent pump-probe spectra with ultrashort XUV and visible/near IR laser pulses in terms of few-fs population transfer at two consecutive conical intersections.

Monitoring of Nonadiabatic Effects in Individual Chromophores by Femtosecond Double-Pump Single-Molecule Spectroscopy: A Model Study.

We explore, by theoretical modeling and computer simulations, how nonadiabatic couplings of excited electronic states of a polyatomic chromophore manifest themselves in single-molecule signals on femtosecond timescales. The chromophore is modeled as a system with three electronic states (the ground state and two non-adiabatically coupled excited states) and a Condon-active vibrational mode which, in turn, is coupled to a harmonic oscillator heat bath. For this system, we simulate double-pump single-molecule signals with fluorescence detection for different system-field interaction strengths, from the weak-coupling regime to the strong-coupling regime. While the signals are determined by the coherence of the electronic density matrix in the weak-coupling regime, they are determined by the populations of the electronic density matrix in the strong-coupling regime. As a consequence, the signals in the strong coupling regime allow the monitoring of nonadiabatic electronic population dynamics and are robust with respect to temporal inhomogeneity of the optical gap, while signals in the weak-coupling regime are sensitive to fluctuations of the optical gap and do not contain information on the electronic population dynamics.

Theoretical calculations about nitro-substituted pyridine as high-energy-density compounds (HEDCs)

A series of derivatives of pyridine were designed through substituting hydrogen atoms by nitro groups systematically. By using the density functional theory at B3PW91/6-311++G(d,p)//MP2/311++G(d,p) level, heats of formation, bond orders, and bond dissociation energies were calculated to explore the thermodynamic stabilities of title molecules. Furthermore, the regularity of stability was explained based on the electronic population. Our results indicated that title molecules had enough stability to exist. To evaluate the potential usage as a high-energy-density molecule, the detonation pressure and detonation velocity were explored by using the semi-empirical Kamlet-Jacobs equation and excellent detonation character was confirmed. Overall consideration of the thermal stability and energetic character, four molecules (2,3,4,5-tetranitropyridine, 2,3,5,6-tetranitropyridine, 2,4,5,6-tetranitrop-pyridine, 2,3,4,5,6-pentanitropyridine) were confirmed to be better than RDX and filtered as potential energetic molecules.

Controlled intramolecular H-transfer in malonaldehyde in the electronic ground state mediated through the conical intersection of 1nπ* and 1ππ* excited electronic states.

We report photo-isomerization of malonaldehyde in its electronic ground state (S0), mediated by coupled 1nπ*(S1)-1ππ*(S2) excited electronic states, accomplished with the aid of optimally designed ultraviolet (UV)-laser pulses. In particular, control of H-transfer from a configuration predominantly located in the left well (say, reactant) to that in the right well (say, product) of the electronic ground S0 potential energy surface is achieved by a pump-dump mechanism including the nonadiabatic interactions between the excited S1 and S2 states. An interplay between the nonadiabatic coupling due to the conical intersection of the S1 and S2 states and the laser-molecule interaction is found to be imprinted in the time-dependent electronic population. The latter is also examined by employing optimal fields of varying intensities and frequencies of the UV laser pulses. For the purpose of the present study, we constructed a three-state and two-mode coupled diabatic Hamiltonian with the help of adiabatic electronic energies and transition dipole moments calculated by ab initio quantum chemistry methods. The electronic diabatic model is developed using the calculated adiabatic energies of the two excited electronic states (S1 and S2) in order to carry out the dynamics study. The optimal fields for achieving the controlled isomerization are designed within the framework of optimal control theory employing the optimization technique of a multitarget functional using the genetic algorithm. The laser-driven dynamics of the system is treated by numerically solving the time-dependent Schrödinger equation within the dipole approximation. A time-averaged yield of the target product of ∼40% is achieved in the present treatment of dynamics with optimal laser pulses.

Analisis Pelayanan Kartu Tanda Penduduk Elektronik untuk Meningkatkan Validitas Data Kependudukan

Government is an organization that protects and serves the entire community in its territory. Thus, service and accountability are worth giving for the welfare of society. The Electronic Population Identity Card (E-KTP) program that is being run has encountered many problems including the process of recording data that has not touched all levels of society and its printing for those who have been recorded constrained because the blanks have run out and have not received supplies from the central government. This study is a descriptive study that uses qualitative methods with normative sociological and empirical juridical approaches. The results of the discussion stated that indeed data recording carried out by the government to date does not reflect the reality in the field. Thus, the government is required to do a data re-tape and provide E-KTP blanks according to regional government data promptly.

First-principles studies of Mg17Al12,Mg2Al3,Mg2Sn,MgZn2,Mg2Ni and Al3Ni phases

Thermal stabilities, electronic structures and elastic properties of Mg2Ni, Al3Ni, Mg2Sn, MgZn2, Mg17Al12 and Mg2Al3 have been determined from first-principle calculations. The calculated results of heats of formation and cohesive energies show that Al3Ni has the strongest alloying ability and structural stability. Gibbs free energy is calculated and discussed. The densities of states (DOS) and Mulliken electronic populations of these compounds are given. The elastic constants are calculated, the bulk moduli, shear moduli, Young's moduli and Poisson ratio value are derived, the brittleness and plasticity of these phases are discussed.

Non-Markovian dynamics of the electronic subsystem in a laser-driven molecule: Characterization and connections with electronic-vibrational entanglement and electronic coherence

Non-Markovian quantum evolution of the electronic subsystem in a laser-driven molecule is characterized through the appearance of negative decoherence rates in the canonical form of the electronic master equation. For a driven molecular system described in a bipartite Hilbert space $\mathcal{H}={\mathcal{H}}_{el}⨂{\mathcal{H}}_{\mathrm{vib}}$ of dimension $2\ifmmode\times\else\texttimes\fi{}{N}_{v}$, we derive the canonical form of the electronic master equation, deducing the canonical measures of non-Markovianity and the Bloch volume of accessible states. We find that one of the decoherence rates is always negative, accounting for the inherent non-Markovian character of the electronic evolution in the vibrational environment. Enhanced non-Markovian behavior, characterized by two negative decoherence rates, appears if there is a coupling between the electronic states $g,\phantom{\rule{0.16em}{0ex}}e$, such that the evolution of the electronic populations obeys $d({P}_{g}{P}_{e})/dt>0$. Non-Markovianity of the electronic evolution is analyzed in relation to temporal behaviors of the electronic-vibrational entanglement and electronic coherence, showing that enhanced non-Markovian behavior accompanies entanglement increase. Taking as an example the coupling of two electronic states by a laser pulse in the ${\mathrm{Cs}}_{2}$ molecule, we analyze non-Markovian dynamics under laser pulses of various strengths, finding that the weaker pulse stimulates the bigger amount of non-Markovianity. Our results show that increase of the electronic-vibrational entanglement over a time interval is correlated to the growth of the total amount of non-Markovianity calculated over the same interval using canonical measures and connected with the increase of the Bloch volume. After the pulse, non-Markovian behavior is correlated to electronic coherence, such that vibrational motion in the electronic potentials which diminishes the nuclear overlap, implicitly increasing the linear entropy of entanglement, brings a memory character to dynamics.

Engineering the color output in a single upconversion microtube via intervention of the electronic population

The engineering of upconversion (UC) light color output is of great importance due to its promising application in biological imaging, data storage and solar cells. In this work, we showed that a tunable red-to-green emission ratio can be achieved by rationally designing the depopulation mechanism of intermediate state via increasing pump power density, pulse duration, pulse interval and Yb3+ concentration accompanied with the waveguide effect in a single Yb3+/Er3+ codoped NaYF4 microtube. We revealed that the red UC luminescence can be enhanced by three-photon process. As expected, three-photon and two-photon processes could be effectively switched by controlling pulse duration and power density. Compared with varying the power density, elevating the Yb concentration accompanied with the waveguide effect is more effective in modifying the color output. Our results provide insight into underlying physical mechanisms of intervening electronic population and present a general approach to constructing a new class of luminescent materials with tunable UC emissions.

Density Functionalized Drug-Surfactant Interaction of Aqueous SDS-Tartrazine

Study of molecular density theory is considered nowadays as a powerful tool to speculate various physical and chemical properties of materials. Herein, we report the theoretical inference of associated changes in chemical properties of sodium dodecyl sulphate and tartrazine when allowed to go through pre- and post-micellization phenomena. Because of the involvement of the two compounds in manifold industrial applications, the study reflects some important conclusions of drug-surfactant chemistry. The computational work involves the use of Polarizable Continuum Model (PCM), water as solvent and 631g(d,p) basis set with B3LYP as functional. Each molecule was run individually first to arrive at an optimized structure followed by a final optimization of assumed network (mesh of proposed binary mixture) to visualize the changes that occur on combination. Each set of energy minimal calculation was then run for frequency calculation, electronic spectral evaluation and molecular natural population analysis. Molecular electrostatic potential surfaces were discussed in linking the appropriate hydrophobic and hydrophilic interaction.

Time-dependent state populations with and without the rotating wave approximation: a model-based study

ABSTRACTWe present a benchmark study by comparing time-dependent electronic state populations calculated in the rotating wave approximation (RWA) to those obtained in numerical exact simulations without the application of the RWA. A wide range of laser intensities and energies are considered in order to explore the limits of the RWA. Our model system consists of a single electron confined to a finite potential well of atomic size so that there are five bound electronic states. The presented numerical study is carried out in the dipole approximation considering either two or all the five electronic states of the system.

Strongly coupled bacteriochlorin dyad studied using phase-modulated fluorescence-detected two-dimensional electronic spectroscopy.

Fluorescence-detected two-dimensional electronic spectroscopy (F-2DES) projects the third-order non-linear polarization in a system as an excited electronic state population which is incoherently detected as fluorescence. Multiple variants of F-2DES have been developed. Here, we report phase-modulated F-2DES measurements on a strongly coupled symmetric bacteriochlorin dyad, a relevant 'toy' model for photosynthetic energy and charge transfer. Coherence map analysis shows that the strongest frequency observed in the dyad is well-separated from the excited state electronic energy gap, and is consistent with a vibrational frequency readily observed in bacteriochlorin monomers. Kinetic rate maps show a picosecond relaxation timescale between the excited states of the dyad. To our knowledge this is the first demonstration of coherence and kinetic analysis using the phase-modulation approach to F-2DES.

Quantum dynamics of multi-dimensional rhodopsin photoisomerization models: Approximate versus accurate treatment of the secondary modes

We numerically investigate the quantum dynamics of the high-dimensional rhodopsin photoisomerization models of Hahn and Stock using the multi-layer multi-configuration time-dependent Hartree (ML-MCTDH) method. The original two-state two-mode model is augmented with additional Raman-active modes observed experimentally and by a bath of low frequency modes that accounts in a generic fashion for the effect the protein and solvent environment. A previously used approximate method in which the two primary modes are treated using an accurate quantum dynamical method while the secondary modes are treated using the time-dependent Hartree (TDH) method is tested against ML-MCTDH calculations. It is shown that the former method does not capture the main effect of these modes on the electronic populations, on the coherent torsional dynamics and on the quantum yield of the photoisomerization reaction. Our ML-MCTDH calculations predict small photoisomerization quantum yields, in contradiction with the experiments, and call for a revision of the model.

The role of the charge-transfer states in the ultrafast excitonic dynamics of the DTDCTB dimers embedded in a crystal environment

Photoinduced excitonic dynamics plays an essential role in the solar energy conversion of organic solar cells. Following our previous work [J. Phys. Chem. C 121 (2017) 27263] on the energy transfer of the 2-[[7-(5-N,N-ditolylaminothiophen-2-yl)-2,1,3-benzothiadiazol-4-yl]methylene]malononitrile (DTDCTB) dimer, we try to understand the role of the intermolecular charge-transfer (CT) electronic states in the excitonic dynamics. When the CT states lie higher than local excited (LE) states and the LE/CT couplings are weak, the CT state plays a minor role. When the LE/CT couplings are strong enough, the CT states start to be unneglectable. When the CT states show lower energies than LE states, the CT states become important. In addition, the near-resonance condition may appear in the excitonic dynamics, resulting in the low-frequency oscillation pattern in the time-dependent electronic populations. This work provides the interesting insight on the role of the CT states in the excitonic dynamics of organic photovoltaic systems.

A Model Medical Student-Led Interprofessional QI Project on Lab Monitoring

Teaching quality improvement (QI) in undergraduate medical education to meet entrustable professional activities (EPA) requirements is a challenge. We describe a model where first-year medical students learn QI methods using online modules and then apply their knowledge by leading an interprofessional project in a clinical setting. This model project, set in an outpatient family medicine clinic, sought to improve patient compliance with the preventive care metric of annual serum potassium and creatinine monitoring for patients taking a diuretic, angiotensin-converting enzyme inhibitor (ACEI), or angiotensin receptor blocker (ARB) medication. A first-year medical student joined an interprofessional team of one primary care physician and three pharmacy residents. The student led the team in reviewing patient charts to identify root causes and implementing a multifaceted strategy to improve patient outreach and refill policies. The effects of these interventions were monitored weekly using an electronic health record population health tool (Epic's Healthy Planet) over the course of 10 months. At baseline, 76.7% (477/622) of patients taking a diuretic and 79.4% (752/947) taking an ACEI or ARB were compliant with monitoring, approximately 10% below the Healthcare Effectiveness Data and Information Set (HEDIS) recommendations. Within 6 months, interventions resulted in both patient cohorts meeting the HEDIS metric with sustained success for the study duration of 10 months. This report demonstrates that a first-year medical student can make meaningful contributions to preventive care while gaining clinically relevant QI experience. Further evaluation is needed to determine generalizability and scalability of this model.

Correction: Epidemiology of complex regional pain syndrome in Korea: An electronic population health data study.

[This corrects the article DOI: 10.1371/journal.pone.0198147.].