On Appel Index of MATH/CHEM/COMP Conference

An index measuring the mathematical content of an interdisciplinary area is described and calculated for the MATH/CHEM/COMP conference. Some further areas of application of this index in mathematical chemistry are indicated

On Appel Index of MATH/CHEM/COMP Conference

An index measuring the mathematical content of an interdisciplinary area is described and calculated for the MATH/CHEM/COMP conference. Some further areas of application of this index in mathematical chemistry are indicated

On the Robustness of Low-frequency Laser Control Schemes for Proton Transfer in Thioacetylacetone

The paper investigates quantum control of the proton transfer reaction in a two-dimensional model system using terahertz (THz) laser fields. The model potential, tailored to MP2 data for thioacetylacetone, comprises the proton transfer and the heavy atom coordinates. Two distinct mechanisms of proton transfer are investigated: the resonant versus the tunneling one. The efficiency of laser control in both cases is tested against the instability of pulse characteristics. The study shows that while the resonant scheme allows efficient control for a large range of field parameters, the tunneling scheme is very sensitive to the pulse characteristics, and therefore experimentally hardly realizable

Dissipative State Selective Vibrational Excitation in Picolinic Acid N-oxide

This paper investigates the effect of Redfield relaxation on the control of state selective excitation in a two-dimensional model system. The model potential, tailored to DFT data for picolinic acid N-oxide, comprises the proton transfer and the heavy atom coordinate. The present Study shows that selective excitation of the O-H stretching mode can be achieved by simple analytical pulses satisfying the n pulse condition. The efficiency of the preparation is tested against the instability of pulse characteristics

Analiza prijenosa energije u međudjelovanju čestice i polja

In this work we have analyzed dynamics of a particle in the one dimensional model of the plane electromagnetic wave. Our particular interest was to show that classical theory can describe this dynamics very well, and gives the correct momentum distribution of particle which depends on the frequency of the field as well as on its amplitude.U ovom radu smo analizirali interakciju čestice i ravnog elektromagnetskog vala. Koristili smo jednodimenzionalnu aproksimaciju. Pokazali smo da u takvoj aproksimaciji, klasična teorija u potpunosti opisuje prijenos energije, te daje respodjelu impulsa koja ovisi prvenstveno o frekvenciji polja

Analiza prijenosa energije u međudjelovanju čestice i polja

In this work we have analyzed dynamics of a particle in the one dimensional model of the plane electromagnetic wave. Our particular interest was to show that classical theory can describe this dynamics very well, and gives the correct momentum distribution of particle which depends on the frequency of the field as well as on its amplitude.U ovom radu smo analizirali interakciju čestice i ravnog elektromagnetskog vala. Koristili smo jednodimenzionalnu aproksimaciju. Pokazali smo da u takvoj aproksimaciji, klasična teorija u potpunosti opisuje prijenos energije, te daje respodjelu impulsa koja ovisi prvenstveno o frekvenciji polja

On the Possible Role of an Intermolecular Charge Transfer State in the Excitation of the Biologically Active Bond of the Retinal Chromophore-counterion Pair

In non-polar solvents the protonation of the all-trans Schiff base of retinal (SBR+) using strong acids leads to formation of retinal chromophore-counterion pairs. Previously we have shown that the main non-reactive deactivation channel of these ion pairs involves internal conversion from the initially excited ππ* state to an inter-molecular charge transfer state (inter-CT) with subsequent dissociation of the chromophore-counterion pair. In solution this leads to the abortion of isomerization. Motivated by the recent X-ray diffraction experiments showing that the disruption of the hydrogen-bonded network of counterions precedes the isomerization of all-trans SBR+ in bacteriorhodopsin we decided to take a closer look at the dynamics of the chromophore-counterion pair in the inter-CT state. Using constrained non-adiabatic dynamics simulations in which the dissociation of the chromophore-counterion pair was impeded, we show that the charge distribution in the inter-CT state leads to site-specific elongation of the biologically active C13=C14 bond. On this basis we hypothesize that an inter-molecular charge transfer state involving the retinal chromophore and the H-bonded counterions (S2) may play an active role in the photoisomerization reaction in a constraint environment. This work is licensed under a Creative Commons Attribution 4.0 International License

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