Philipp Marquetand | University of Vienna (original) (raw)
Papers by Philipp Marquetand
Proceedings of the 70th International Symposium on Molecular Spectroscopy, 2015
Journal of the American Chemical Society, Jan 12, 2015
The excited-state dynamics of the purine free base and 9 methylpurine are investigated using expe... more The excited-state dynamics of the purine free base and 9 methylpurine are investigated using experimental and theoretical methods. Femtosecond broadband transient absorption experiments reveal that excitation of these purine derivatives in aqueous solution at 266 nm results primarily in ultrafast conversion of the S2(ππ*) state to the vibrationally-excited 1nπ* state. Following vibrational and conformational relaxation, the 1nπ* state acts as a doorway state in the efficient population of the triplet manifold with an intersystem crossing lifetime of hundreds of picoseconds. Experiments in polar aprotic and nonpolar solvents show an almost twofold increase in the intersystem crossing rate, suggesting that a solvent-dependent energy barrier must be surmounted to access the singlet-to-triplet crossing region. Ab initio static and surface hopping dynamics simulations lend strong support to the proposed relaxation mechanism. Collectively, the experimental and computational results demons...
Journal of the American Chemical Society
The excited-state dynamics of the purine free base and 9 methylpurine are investigated using expe... more The excited-state dynamics of the purine free base and 9 methylpurine are investigated using experimental and theoretical methods. Femtosecond broadband transient absorption experiments reveal that excitation of these purine derivatives in aqueous solution at 266 nm results primarily in ultrafast conversion of the S2(ππ*) state to the vibrationally-excited 1nπ* state. Following vibrational and conformational relaxation, the 1nπ* state acts as a doorway state in the efficient population of the triplet manifold with an intersystem crossing lifetime of hundreds of picoseconds. Experiments in polar aprotic and nonpolar solvents show an almost twofold increase in the intersystem crossing rate, suggesting that a solvent-dependent energy barrier must be surmounted to access the singlet-to-triplet crossing region. Ab initio static and surface hopping dynamics simulations lend strong support to the proposed relaxation mechanism. Collectively, the experimental and computational results demons...
The Journal of Chemical Physics, 2004
We regard the rovibrational wave packet dynamics of NaI in a static electric field after femtosec... more We regard the rovibrational wave packet dynamics of NaI in a static electric field after femtosecond excitation to its first electronically excited state. The following quasibound nuclear wave packet motion is accompanied by a bonding situation changing from covalent to ionic. At times when the charge separation is present, i.e., when the bond-length is large, a strong dipole moment exists and rotational excitation takes place. Upon bond contraction, the then covalently bound molecule does not experience the external field. This scenario repeats itself periodically. Thus, the vibrational dynamics causes a situation which is comparable to the interaction of the molecule with a train of pulses where the pulse separation is determined by the vibrational period.
Phys. Chem. Chem. Phys., 2015
An extended designed regression analysis of experimental data on density and refractive indices o... more An extended designed regression analysis of experimental data on density and refractive indices of several classes of ionic liquids yielded statistically averaged atomic volumes and polarizabilities of the constituting atoms. These values can be used to predict the molecular volume and polarizability of an unknown ionic liquid as well as its mass density and refractive index. Our approach does not need information on the molecular structure of the ionic liquid, but it turned out that the discrimination of the hybridization state of the carbons improved the overall result. Our results are not only compared to experimental data but also to quantum-chemical calculations. Furthermore, fractional charges of ionic liquid ions and their relation to polarizability are discussed.
Journal of Chemical Theory and Computation, 2015
Artificial neural networks (NNs) represent a relatively recent approach for the prediction of mol... more Artificial neural networks (NNs) represent a relatively recent approach for the prediction of molecular potential energies, suitable for simulations of large molecules and long time scales. By using NNs to fit electronic structure data, it is possible to obtain empirical potentials of high accuracy combined with the computational efficiency of conventional force fields. However, as opposed to the latter, changing bonding patterns and unusual coordination geometries can be described due to the underlying flexible functional form of the NNs. One of the most promising approaches in this field is the high-dimensional neural network (HDNN) method, which is especially adapted to the prediction of molecular properties. While HDNNs have been mostly used to model solid state systems and surface interactions, we present here the first application of the HDNN approach to an organic reaction, the Claisen rearrangement of allyl vinyl ether to 4-pentenal. To construct the corresponding HDNN potential, a new training algorithm is introduced. This algorithm is termed "element-decoupled" global extended Kalman filter (ED-GEKF) and is based on the decoupled Kalman filter. Using a metadynamics trajectory computed with density functional theory as reference data, we show that the ED-GEKF exhibits superior performance - both in terms of accuracy and training speed - compared to other variants of the Kalman filter hitherto employed in HDNN training. In addition, the effect of including forces during ED-GEKF training on the resulting potentials was studied.
ABSTRACT The importance of triplet states in the photorelaxation dynamics of SO2 is studied by mi... more ABSTRACT The importance of triplet states in the photorelaxation dynamics of SO2 is studied by mixed quantum-classical dynamics simulations. Using the Surface Hopping including ARbitrary Couplings (Sharc) method, intersystem crossing processes caused by spin-orbit coupling are found occuring on an ultrafast time scale (below 100 fs) and thus competing with internal conversion. Comparing the dynamics including singlet and triplet states to the singlet-only dynamics, very different results are obtained for the populations of the respective states. However, the vibrational motion in the triplet manifold very much resembles the one in the singlet manifold. Consequently, the contribution of the triplet states may be difficult to detect in a broad range of experiments.
Proceedings of the 70th International Symposium on Molecular Spectroscopy, 2015
The Journal of Physical Chemistry A, 2015
Accurate excited-state quantum chemical calculations on 2-thiouracil, employing large active spac... more Accurate excited-state quantum chemical calculations on 2-thiouracil, employing large active spaces and up to quadruple-ζ quality basis sets in multistate complete active space perturbation theory calculations, are reported. The results suggest that the main relaxation path for 2-thiouracil after photoexcitation should be S2 → S1 → T2 → T1, and that this relaxation occurs on a subpicosecond time scale. There are two deactivation pathways from the initially excited bright S2 state to S1, one of which is nearly barrierless and should promote ultrafast internal conversion. After relaxation to the S1 minimum, small singlet-triplet energy gaps and spin-orbit couplings of about 130 cm(-1) are expected to facilitate intersystem crossing to T2, from where very fast internal conversion to T1 occurs. An important finding is that 2-thiouracil shows strong pyramidalization at the carbon atom of the thiocarbonyl group in several excited states.
International Journal of Quantum Chemistry, 2015
ABSTRACT Intersystem crossing is a radiationless process that can take place in a molecule irradi... more ABSTRACT Intersystem crossing is a radiationless process that can take place in a molecule irradiated by UV-Vis light, thereby playing an important role in many environmental, biological and technological processes. This paper reviews different methods to describe intersystem crossing dynamics, paying attention to semiclassical trajectory theories, which are especially interesting because they can be applied to large systems with many degrees of freedom. In particular, a general trajectory surface hopping methodology recently developed by the authors, which is able to include nonadiabatic and spin-orbit couplings in excited-state dynamics simulations, is explained in detail. This method, termed SHARC, can in principle include any arbitrary coupling, what makes it generally applicable to photophysical and photochemical problems, also those including explicit laser fields. A step-by-step derivation of the main equations of motion employed in surface hopping based on the fewest-switches method of Tully, adapted for the inclusion of spin-orbit interactions, is provided. Special emphasis is put on describing the different possible choices of the electronic bases in which spin-orbit can be included in surface hopping, highlighting the advantages and inconsistencies of the different approaches. © 2015 Wiley Periodicals, Inc.
The Journal of chemical physics, Jan 28, 2014
The importance of triplet states in the photorelaxation dynamics of SO2 is studied by mixed quant... more The importance of triplet states in the photorelaxation dynamics of SO2 is studied by mixed quantum-classical dynamics simulations. Using the SHARC method, standing for Surface Hopping including ARbitrary Couplings, intersystem crossing (ISC) processes caused by spin-orbit coupling are found occurring on an ultrafast time scale (few 100 fs) and thus competing with internal conversion. While in the singlet-only dynamics only oscillatory population transfer between the (1)B1 and (1)A2 states is observed, in the dynamics including singlet and triplet states we find additionally continuous ISC to the (3)B2 state and to a smaller extent to the (3)B1/(3)A2 coupled states. The populations obtained from the dynamics are discussed with respect to the overall nuclear motion and in the light of recent TRPEPICO studies [I. Wilkinson, A. E. Boguslavskiy, J. Mikosch, D. M. Villeneuve, H.-J. Wörner, M. Spanner, S. Patchkovskii, and A. Stolow, "Excited state dynamics in SO2. I. Bound state rel...
Journal of the American Chemical Society, Jan 12, 2015
The excited-state dynamics of the purine free base and 9 methylpurine are investigated using expe... more The excited-state dynamics of the purine free base and 9 methylpurine are investigated using experimental and theoretical methods. Femtosecond broadband transient absorption experiments reveal that excitation of these purine derivatives in aqueous solution at 266 nm results primarily in ultrafast conversion of the S2(ππ*) state to the vibrationally-excited 1nπ* state. Following vibrational and conformational relaxation, the 1nπ* state acts as a doorway state in the efficient population of the triplet manifold with an intersystem crossing lifetime of hundreds of picoseconds. Experiments in polar aprotic and nonpolar solvents show an almost twofold increase in the intersystem crossing rate, suggesting that a solvent-dependent energy barrier must be surmounted to access the singlet-to-triplet crossing region. Ab initio static and surface hopping dynamics simulations lend strong support to the proposed relaxation mechanism. Collectively, the experimental and computational results demons...
ABSTRACT The importance of triplet states in the photorelaxation dynamics of SO2 is studied by mi... more ABSTRACT The importance of triplet states in the photorelaxation dynamics of SO2 is studied by mixed quantum-classical dynamics simulations. Using the Surface Hopping including ARbitrary Couplings (Sharc) method, intersystem crossing processes caused by spin-orbit coupling are found occuring on an ultrafast time scale (below 100 fs) and thus competing with internal conversion. Comparing the dynamics including singlet and triplet states to the singlet-only dynamics, very different results are obtained for the populations of the respective states. However, the vibrational motion in the triplet manifold very much resembles the one in the singlet manifold. Consequently, the contribution of the triplet states may be difficult to detect in a broad range of experiments.
19th International Conference on Ultrafast Phenomena, 2014
ABSTRACT Mixed quantum-classical dynamics simulations show that intersystem crossing between sing... more ABSTRACT Mixed quantum-classical dynamics simulations show that intersystem crossing between singlet and triplet states in SO2 and in nucleobases takes place on an ultrafast time decay (few 100 fs), directly competing with internal conversion.
Topics in current chemistry, 2015
This chapter is devoted to unravel the relaxation processes taking place after photoexcitation of... more This chapter is devoted to unravel the relaxation processes taking place after photoexcitation of isolated DNA/RNA nucleobases in gas phase from a time-dependent perspective. To this aim, several methods are at hand, ranging from full quantum dynamics to various flavours of semiclassical or ab initio molecular dynamics, each with its advantages and its limitations. As this contribution shows, the most common approach employed up to date to learn about the deactivation of nucleobases in gas phase is a combination of the Tully surface hopping algorithm with on-the-fly CASSCF calculations. Different dynamics methods or, even more dramatically, different electronic structure methods can provide different dynamics. A comprehensive review of the different mechanisms suggested for each nucleobase is provided and compared to available experimental time scales. The results are discussed in a general context involving the effects of the different applied electronic structure and dynamics meth...
Proceedings of the 70th International Symposium on Molecular Spectroscopy, 2015
Journal of the American Chemical Society, Jan 12, 2015
The excited-state dynamics of the purine free base and 9 methylpurine are investigated using expe... more The excited-state dynamics of the purine free base and 9 methylpurine are investigated using experimental and theoretical methods. Femtosecond broadband transient absorption experiments reveal that excitation of these purine derivatives in aqueous solution at 266 nm results primarily in ultrafast conversion of the S2(ππ*) state to the vibrationally-excited 1nπ* state. Following vibrational and conformational relaxation, the 1nπ* state acts as a doorway state in the efficient population of the triplet manifold with an intersystem crossing lifetime of hundreds of picoseconds. Experiments in polar aprotic and nonpolar solvents show an almost twofold increase in the intersystem crossing rate, suggesting that a solvent-dependent energy barrier must be surmounted to access the singlet-to-triplet crossing region. Ab initio static and surface hopping dynamics simulations lend strong support to the proposed relaxation mechanism. Collectively, the experimental and computational results demons...
Journal of the American Chemical Society
The excited-state dynamics of the purine free base and 9 methylpurine are investigated using expe... more The excited-state dynamics of the purine free base and 9 methylpurine are investigated using experimental and theoretical methods. Femtosecond broadband transient absorption experiments reveal that excitation of these purine derivatives in aqueous solution at 266 nm results primarily in ultrafast conversion of the S2(ππ*) state to the vibrationally-excited 1nπ* state. Following vibrational and conformational relaxation, the 1nπ* state acts as a doorway state in the efficient population of the triplet manifold with an intersystem crossing lifetime of hundreds of picoseconds. Experiments in polar aprotic and nonpolar solvents show an almost twofold increase in the intersystem crossing rate, suggesting that a solvent-dependent energy barrier must be surmounted to access the singlet-to-triplet crossing region. Ab initio static and surface hopping dynamics simulations lend strong support to the proposed relaxation mechanism. Collectively, the experimental and computational results demons...
The Journal of Chemical Physics, 2004
We regard the rovibrational wave packet dynamics of NaI in a static electric field after femtosec... more We regard the rovibrational wave packet dynamics of NaI in a static electric field after femtosecond excitation to its first electronically excited state. The following quasibound nuclear wave packet motion is accompanied by a bonding situation changing from covalent to ionic. At times when the charge separation is present, i.e., when the bond-length is large, a strong dipole moment exists and rotational excitation takes place. Upon bond contraction, the then covalently bound molecule does not experience the external field. This scenario repeats itself periodically. Thus, the vibrational dynamics causes a situation which is comparable to the interaction of the molecule with a train of pulses where the pulse separation is determined by the vibrational period.
Phys. Chem. Chem. Phys., 2015
An extended designed regression analysis of experimental data on density and refractive indices o... more An extended designed regression analysis of experimental data on density and refractive indices of several classes of ionic liquids yielded statistically averaged atomic volumes and polarizabilities of the constituting atoms. These values can be used to predict the molecular volume and polarizability of an unknown ionic liquid as well as its mass density and refractive index. Our approach does not need information on the molecular structure of the ionic liquid, but it turned out that the discrimination of the hybridization state of the carbons improved the overall result. Our results are not only compared to experimental data but also to quantum-chemical calculations. Furthermore, fractional charges of ionic liquid ions and their relation to polarizability are discussed.
Journal of Chemical Theory and Computation, 2015
Artificial neural networks (NNs) represent a relatively recent approach for the prediction of mol... more Artificial neural networks (NNs) represent a relatively recent approach for the prediction of molecular potential energies, suitable for simulations of large molecules and long time scales. By using NNs to fit electronic structure data, it is possible to obtain empirical potentials of high accuracy combined with the computational efficiency of conventional force fields. However, as opposed to the latter, changing bonding patterns and unusual coordination geometries can be described due to the underlying flexible functional form of the NNs. One of the most promising approaches in this field is the high-dimensional neural network (HDNN) method, which is especially adapted to the prediction of molecular properties. While HDNNs have been mostly used to model solid state systems and surface interactions, we present here the first application of the HDNN approach to an organic reaction, the Claisen rearrangement of allyl vinyl ether to 4-pentenal. To construct the corresponding HDNN potential, a new training algorithm is introduced. This algorithm is termed "element-decoupled" global extended Kalman filter (ED-GEKF) and is based on the decoupled Kalman filter. Using a metadynamics trajectory computed with density functional theory as reference data, we show that the ED-GEKF exhibits superior performance - both in terms of accuracy and training speed - compared to other variants of the Kalman filter hitherto employed in HDNN training. In addition, the effect of including forces during ED-GEKF training on the resulting potentials was studied.
ABSTRACT The importance of triplet states in the photorelaxation dynamics of SO2 is studied by mi... more ABSTRACT The importance of triplet states in the photorelaxation dynamics of SO2 is studied by mixed quantum-classical dynamics simulations. Using the Surface Hopping including ARbitrary Couplings (Sharc) method, intersystem crossing processes caused by spin-orbit coupling are found occuring on an ultrafast time scale (below 100 fs) and thus competing with internal conversion. Comparing the dynamics including singlet and triplet states to the singlet-only dynamics, very different results are obtained for the populations of the respective states. However, the vibrational motion in the triplet manifold very much resembles the one in the singlet manifold. Consequently, the contribution of the triplet states may be difficult to detect in a broad range of experiments.
Proceedings of the 70th International Symposium on Molecular Spectroscopy, 2015
The Journal of Physical Chemistry A, 2015
Accurate excited-state quantum chemical calculations on 2-thiouracil, employing large active spac... more Accurate excited-state quantum chemical calculations on 2-thiouracil, employing large active spaces and up to quadruple-ζ quality basis sets in multistate complete active space perturbation theory calculations, are reported. The results suggest that the main relaxation path for 2-thiouracil after photoexcitation should be S2 → S1 → T2 → T1, and that this relaxation occurs on a subpicosecond time scale. There are two deactivation pathways from the initially excited bright S2 state to S1, one of which is nearly barrierless and should promote ultrafast internal conversion. After relaxation to the S1 minimum, small singlet-triplet energy gaps and spin-orbit couplings of about 130 cm(-1) are expected to facilitate intersystem crossing to T2, from where very fast internal conversion to T1 occurs. An important finding is that 2-thiouracil shows strong pyramidalization at the carbon atom of the thiocarbonyl group in several excited states.
International Journal of Quantum Chemistry, 2015
ABSTRACT Intersystem crossing is a radiationless process that can take place in a molecule irradi... more ABSTRACT Intersystem crossing is a radiationless process that can take place in a molecule irradiated by UV-Vis light, thereby playing an important role in many environmental, biological and technological processes. This paper reviews different methods to describe intersystem crossing dynamics, paying attention to semiclassical trajectory theories, which are especially interesting because they can be applied to large systems with many degrees of freedom. In particular, a general trajectory surface hopping methodology recently developed by the authors, which is able to include nonadiabatic and spin-orbit couplings in excited-state dynamics simulations, is explained in detail. This method, termed SHARC, can in principle include any arbitrary coupling, what makes it generally applicable to photophysical and photochemical problems, also those including explicit laser fields. A step-by-step derivation of the main equations of motion employed in surface hopping based on the fewest-switches method of Tully, adapted for the inclusion of spin-orbit interactions, is provided. Special emphasis is put on describing the different possible choices of the electronic bases in which spin-orbit can be included in surface hopping, highlighting the advantages and inconsistencies of the different approaches. © 2015 Wiley Periodicals, Inc.
The Journal of chemical physics, Jan 28, 2014
The importance of triplet states in the photorelaxation dynamics of SO2 is studied by mixed quant... more The importance of triplet states in the photorelaxation dynamics of SO2 is studied by mixed quantum-classical dynamics simulations. Using the SHARC method, standing for Surface Hopping including ARbitrary Couplings, intersystem crossing (ISC) processes caused by spin-orbit coupling are found occurring on an ultrafast time scale (few 100 fs) and thus competing with internal conversion. While in the singlet-only dynamics only oscillatory population transfer between the (1)B1 and (1)A2 states is observed, in the dynamics including singlet and triplet states we find additionally continuous ISC to the (3)B2 state and to a smaller extent to the (3)B1/(3)A2 coupled states. The populations obtained from the dynamics are discussed with respect to the overall nuclear motion and in the light of recent TRPEPICO studies [I. Wilkinson, A. E. Boguslavskiy, J. Mikosch, D. M. Villeneuve, H.-J. Wörner, M. Spanner, S. Patchkovskii, and A. Stolow, "Excited state dynamics in SO2. I. Bound state rel...
Journal of the American Chemical Society, Jan 12, 2015
The excited-state dynamics of the purine free base and 9 methylpurine are investigated using expe... more The excited-state dynamics of the purine free base and 9 methylpurine are investigated using experimental and theoretical methods. Femtosecond broadband transient absorption experiments reveal that excitation of these purine derivatives in aqueous solution at 266 nm results primarily in ultrafast conversion of the S2(ππ*) state to the vibrationally-excited 1nπ* state. Following vibrational and conformational relaxation, the 1nπ* state acts as a doorway state in the efficient population of the triplet manifold with an intersystem crossing lifetime of hundreds of picoseconds. Experiments in polar aprotic and nonpolar solvents show an almost twofold increase in the intersystem crossing rate, suggesting that a solvent-dependent energy barrier must be surmounted to access the singlet-to-triplet crossing region. Ab initio static and surface hopping dynamics simulations lend strong support to the proposed relaxation mechanism. Collectively, the experimental and computational results demons...
ABSTRACT The importance of triplet states in the photorelaxation dynamics of SO2 is studied by mi... more ABSTRACT The importance of triplet states in the photorelaxation dynamics of SO2 is studied by mixed quantum-classical dynamics simulations. Using the Surface Hopping including ARbitrary Couplings (Sharc) method, intersystem crossing processes caused by spin-orbit coupling are found occuring on an ultrafast time scale (below 100 fs) and thus competing with internal conversion. Comparing the dynamics including singlet and triplet states to the singlet-only dynamics, very different results are obtained for the populations of the respective states. However, the vibrational motion in the triplet manifold very much resembles the one in the singlet manifold. Consequently, the contribution of the triplet states may be difficult to detect in a broad range of experiments.
19th International Conference on Ultrafast Phenomena, 2014
ABSTRACT Mixed quantum-classical dynamics simulations show that intersystem crossing between sing... more ABSTRACT Mixed quantum-classical dynamics simulations show that intersystem crossing between singlet and triplet states in SO2 and in nucleobases takes place on an ultrafast time decay (few 100 fs), directly competing with internal conversion.
Topics in current chemistry, 2015
This chapter is devoted to unravel the relaxation processes taking place after photoexcitation of... more This chapter is devoted to unravel the relaxation processes taking place after photoexcitation of isolated DNA/RNA nucleobases in gas phase from a time-dependent perspective. To this aim, several methods are at hand, ranging from full quantum dynamics to various flavours of semiclassical or ab initio molecular dynamics, each with its advantages and its limitations. As this contribution shows, the most common approach employed up to date to learn about the deactivation of nucleobases in gas phase is a combination of the Tully surface hopping algorithm with on-the-fly CASSCF calculations. Different dynamics methods or, even more dramatically, different electronic structure methods can provide different dynamics. A comprehensive review of the different mechanisms suggested for each nucleobase is provided and compared to available experimental time scales. The results are discussed in a general context involving the effects of the different applied electronic structure and dynamics meth...