Time-Dependent Expectation Values from Integral Equations for Quantum Flux and Probability Densities.

We compare the calculation of time-dependent quantum expectation values performed in different ways. In one case, they are obtained from an integral over a function of the probability density, and in the other case, the integral is over a function of the probability flux density. The two kinds of coordinate-dependent integrands are very different in their appearance, but integration yields identical results, if the exact wave function enters into the computation. This can be different, if one applies approximations to the wave function. For illustration, we treat one- and two-dimensional dynamics in coupled electron-nuclear systems. Using the adiabatic expansion of the total wave function, the expectation values are decomposed into different contributions. This allows us to discuss the validity of the Born-Oppenheimer (BO) approximation applied to the calculation of the expectation values from probability density- and flux density- integrals. Choosing force- and torque operators as examples, we illustrate the different spatiotemporal characteristics of the various integrands.

Optically Induced Charge Transfer in Organic Mixed-Valence Systems: Wave Packet Dynamics and Femtosecond Transient Spectroscopy.

We theoretically study the dynamics of charge transfer induced by femtosecond laser-pulse excitation. Models involving coupled electronic states of symmetrically bridged organic mixed-valence molecules are investigated, where the motion proceeds along two reaction coordinates. Linear absorption spectra of two species that differ in the energetical position of the bridge, relative to acceptor and donor states, are determined and compared to experimental results. From the wave packet dynamics it emerges that relaxation dominates the charge transfer. This behavior is reflected in transient absorption spectra, which are obtained from a directional decomposition of the time-dependent polarization. Due to the nature of the coupled dynamics the extraction of the relevant contributions needs an extension of well-known techniques for the decomposition.

Exciton-exciton annihilation in a molecular trimer: Wave packet dynamics and 2D spectroscopy.

We theoretically study the exciton-exciton annihilation (EEA) in a molecular trimer MMM. The system is treated within a model of electronic states, and the coupling to a bath is incorporated using the quantum jump method. Two situations of initial excitation are compared. In the first one, a two-photon process populates configurations M*M*M and MM*M* so that two excitons reside on neighboring monomers M. Then, EEA can immediately proceed. In contrast, if the trimer initially is in the local configuration M*MM*, exciton diffusion must occur before the annihilation process can take place. For the trimer, this excitonic motion takes place on a very short time scale. In both cases, wave packets are prepared which show a different quantum dynamics where the latter depends on the couplings and decay rates. It is documented how fifth-order coherent two-dimensional spectroscopy can be used to directly map the EEA as a function of time.

A wave packet picture of exciton-exciton annihilation: Molecular dimer dynamics.

The usual view of exciton-exciton annihilation (EEA) processes in molecular aggregates is based on locally excited states of the monomer units. However, the corresponding localized configurations can only be assumed if the system is in a coherent superposition of eigenstates, i.e., a wave packet. We study a molecular dimer and focus on the characterization of EEA by a wave packet motion induced in the system by ultrashort pulse excitation. Here, coherences that appear are destroyed by dissipation processes. We discuss the influence of interband and intraband relaxation on the dynamics. The states that participate in the annihilation process are directly accessible by fifth-order optical two-dimensional spectroscopy. Such spectra are calculated, and spectral features are related to the annihilation process.

Mapping of exciton-exciton annihilation in a molecular dimer via fifth-order femtosecond two-dimensional spectroscopy.

We present a theoretical study on exciton-exciton annihilation (EEA) in a molecular dimer. This process is monitored using a fifth-order coherent two-dimensional (2D) spectroscopy as was recently proposed by Dostál et al. [Nat. Commun. 9, 2466 (2018)]. Using an electronic three-level system for each monomer, we analyze the different paths which contribute to the 2D spectrum. The spectrum is determined by two entangled relaxation processes, namely, the EEA and the direct relaxation of higher lying excited states. It is shown that the change of the spectrum as a function of a pulse delay can be linked directly to the presence of the EEA process.

How fast is optically induced electron transfer in organic mixed valence systems?

The rate of thermally induced electron transfer in organic mixed valence compounds has thoroughly been investigated by e.g. temperature dependent ESR spectroscopy. However, almost nothing is known about the dynamics of optically induced electron transfer processes in such systems. Therefore, we investigated these processes in mixed valence compounds based on triphenylamine redox centres bridged by conjugated spacers by NIR transient absorption spectroscopy with fs-time resolution. These experiments revealed an internal conversion (IC) process to be on the order of 50-200 fs which is equivalent to the back electron transfer after optical excitation into the intervalence charge transfer band. This IC is followed by ultrafast cooling to the ground state within 1 ps. Thus, in the systems investigated optically induced electron transfer is about 3-4 orders of magnitude faster than thermally induced ET.

Two-dimensional vibronic spectroscopy of molecular aggregates: Trimers, dimers, and monomers.

The two-dimensional (2D) vibronic spectroscopy of molecular trimers is studied theoretically. The solution of the time-dependent Schrödinger equation is carried out with the multi-configurational time-dependent Hartree (MCTDH) method which allows for an efficient propagation of the multi-component wave functions. 2D-spectra are calculated for H- and J-type aggregates incorporating one or two vibrational modes for each monomer. In performing calculations for monomer, dimer, and trimer systems, it is documented how the vibronic structure of the 2D-spectrum changes upon aggregation. This is of importance for the characterization of aggregation behavior being influenced by experimental conditions such as temperature or concentration.

Coherent and incoherent contributions to the carrier-envelope phase control of wave packet localization in quantum double wells.

We study laser excitation processes in a double well potential. The possibility to influence localization via the carrier-envelope phase (CEP) of a laser pulse is investigated for various situations which differ in the nature of the initial state prior to the laser interactions. In more detail, the CEP-dependence of asymmetries in the case where initially the system is described by localized wave packets, eigenstates, or incoherent mixtures are calculated and interpreted within time-dependent perturbation theory. It is investigated which contributions to the asymmetry exist and how they can be modified to reveal a more or less pronounced CEP-effect.

Differential Shannon Entropies and Mutual Information in a Curve Crossing System: Adiabatic and Diabatic Decompositions.

The differential Shannon entropy provides a measure for the localization of a wave function. We regard the vibrational wave packet motion in a curve crossing system and calculate time-dependent entropies. Using a numerical example, we analyze how localization inside diabatic and adiabatic states can be accessed and discuss the differences between these two representations. In order to do so, we extend the usual entropy definition and introduce novel state-selective entropies. These quantities contain information on the form of the nuclear density components on the one hand and on the state population on the other, and it is shown how the contribution of the population can be removed. Having the state-selective entropies at hand, two additional functions derived from these, namely, the conditional entropy and the mutual information, are determined and compared. We find that these quantities relate closely to correlation effects rooted in different electronic properties of the system.

On the parameterization of vibronic Hamiltonians for molecular aggregates using absorption line-shapes as an input.

Absorption line-shapes of molecular aggregates are often calculated using a simple form for a vibronic Hamiltonian. Parameters which enter into the model are usually taken from measured spectra. Here, we address the question in how far different sets of input parameters used to calculate the spectra lead to similar spectral features. Therefore, we first present analytical expressions which illustrate the relation between the various parameters such as Huang-Rhys factors, electronic coupling elements, and aggregate size. Numerical calculations show that identical peak ratios and spectra can be obtained for different sets of parameters. This illustrates the basic difficulties in extracting reliable molecular information from a comparison of calculated and measured spectra.

Dissipative wave packet dynamics of hydrophobic → hydrophilic site switching in phenol-Ar clusters.

We analyze the results of recent pump-probe experiments on the site-switching dynamics of Ar within cationic phenol-Ar(2) clusters. A reaction-path model is employed for the wave packet dynamics. It is shown that the mechanism of energy dissipation is to be included to understand the features of the transient signals. Therefore, a simple recipe to include energy relaxation to the quantum dynamics is introduced. It is then possible to reproduce the measured pump-probe signals by adjustment of only two parameters.

Vibronic transitions and quantum dynamics in molecular oligomers: a theoretical analysis with an application to aggregates of perylene bisimides.

Vibronic absorption spectra of molecular aggregates consisting of up to N = 9 monomer units are calculated employing methods of time-dependent quantum mechanics. Taking one vibrational degree of freedom for each monomer into account and treating one-exciton excited electronic states leads to a problem with N vibrations and N electronically coupled states. The demanding quantum propagation is carried out within the multiconfiguration time-depended Hartree method (MCTDH). Spectral features of and population transfer in the aggregates are analyzed as a function of the aggregate size and the strength of the electronic coupling. With a model for oligomers of perylene bisimides, it is shown how measured temperature-dependent absorption spectra correlate with the aggregate size. Furthermore, the exciton localization and dynamics in these aggregates are investigated.

Quantum study of the absorption spectroscopy of bis(triarylamine) radical cations.

Absorption spectra of bridged triarylamine radical cations are calculated quantum mechanically which extends our previous classical analysis (Lambert et al. J. Phys. Chem. A 2004, 108, 6474). A comparison between spectra determined within a diabatic and an adiabatic representation shows that under certain circumstances deviations occur. It is found that the latter are mainly caused by the Condon approximation for the dipole moments. The inclusion of vibrational degrees of freedom leads to an excellent agreement with experiment.

Immunogenicity of oncolytic vaccinia viruses JX-GFP and TG6002 in a human melanoma in vitro model: studying immunogenic cell death, dendritic cell maturation and interaction with cytotoxic T lymphocytes.

Oncolytic virotherapy is an emerging immunotherapeutic modality for cancer treatment. Oncolytic viruses with genetic modifications can further enhance the oncolytic effects on tumor cells and stimulate antitumor immunity. The oncolytic vaccinia viruses JX-594-GFP+/hGM-CSF (JX-GFP) and TG6002 are genetically modified by secreting granulocyte-macrophage colony-stimulating factor (GM-CSF) or transforming 5-fluorocytosine (5-FC) into 5-fluorouracil (5-FU). We compared their properties to kill tumor cells and induce an immunogenic type of cell death in a human melanoma cell model using SK29-MEL melanoma cells. Their influence on human immune cells, specifically regarding the activation of dendritic cells (DCs) and the interaction with the autologous cytotoxic T lymphocyte (CTL) clone, was investigated. Melanoma cells were infected with either JX-GFP or TG6002 alone or in combination with 5-FC and 5-FU. The influence of viral infection on cell viability followed a time- and multiplicity of infection dependent manner. Combination of virus treatment with 5-FU resulted in stronger reduction of cell viability. TG6002 in combination with 5-FC did not significantly strengthen the reduction of cell viability in this setting. Expression of calreticulin and high mobility group 1 protein (HMGB1), markers of immunogenic cell death (ICD), could be detected after viral infection. Accordingly, DC maturation was noted after viral oncolysis. DCs presented stronger expression of activation and maturation markers. The autologous CTL clone IVSB expressed the activation marker CD69, but viral treatment failed to enhance cytotoxicity marker. In summary, vaccinia viruses JX-GFP and TG6002 lyse melanoma cells and induce additional immunostimulatory effects to promote antitumor immune response. Further investigation in vivo is needed to consolidate the data.

Exciton dynamics in perturbed vibronic molecular aggregates.

A site specific perturbation of a photo-excited molecular aggregate can lead to a localization of excitonic energy. We investigate this localization dynamics for laser-prepared excited states. Changing the parameters of the electric field significantly influences the exciton localization which offers the possibility for a selective control of this process. This is demonstrated for aggregates possessing a single vibrational degree of freedom per monomer unit. It is shown that the effects identified for the molecular dimer can be generalized to larger aggregates with a high density of vibronic states.

Phase-space analysis of double ionization.

We use the Wigner transformation to study the electronic center-of-mass motion in phase-space for double ionization in a strong laser field. The rescattering mechanism is clearly visible in the evolution of the fully correlated two-electron system. In a mean-field calculation, on the other hand, the signatures of rescattering are missing. Some properties of the Wigner function in two-particle systems are reported.

Intense-field double ionization of helium: identifying the mechanism

We present quantum mechanical calculations of the electron and ion momentum distributions following double ionization of a one-dimensional helium atom by ultrashort laser pulses (780 nm) at various intensities. The two-electron momentum distributions exhibit a clear transition from nonsequential to sequential double ionization. We provide strong evidence that rescattering is responsible for nonsequential ionization by calculating the momentum spectrum of the He2+ recoil ions-which we find in excellent agreement with recent experiments-and by analyzing the electronic center-of-mass motion via Wigner transforms.

Stent-free tubularized incised plate (TIP) repair of distal and mid-shaft hypospadias irrespective of age.

PURPOSE: Aim of this study was to report our experiences with tubularized incised plate (TIP) repair without placement of a postoperative urethral stent in 41 cases. PATIENTS AND METHODS: Since October 2005, we have performed TIP repair for distal penile hypospadias without using a postoperative urethral stent. A urethral stent is used intraoperatively for the tubularization of the neourethra and is removed at the end of the procedure. Follow-up included clinical examination and a structured telephone interview on parental satisfaction. RESULTS: The group included 41 boys, 60% with coronal or distal hypospadias and 40% with mid-shaft hypospadias (aged 6 months to 16 years, median: 3 years). In 7 cases, the prepuce was also reconstructed. There were 2 cases with fistula and one case of meatal stenosis. No glans dehiscence, severe bleeding, or wound infection was observed. No urinary retention requiring catheterization was observed, irrespective of age. All but one patient was discharged the day after surgery. Follow-up ranged from 8 to 48 months (average: 22 months). Most parents (87.5%) were satisfied or very satisfied. CONCLUSION: Based on our preliminary experiences, patient comfort and safety, parental satisfaction and the rate of complications seem to be promising with this technique.