Page 1. 8 Observing molecular structure changes and dynamics in polar solutionAlexander L. Dobrya... more Page 1. 8 Observing molecular structure changes and dynamics in polar solutionAlexander L. Dobryakov1, Nikolaus P. Ernsting1, Wojciech Gawelda2, Christian Bressler2, Majed Chergui2 1 Department of Chemistry, Humboldt ...
ABSTRACT We present our new results exploiting simultaneously picosecond and femtosecond x-ray em... more ABSTRACT We present our new results exploiting simultaneously picosecond and femtosecond x-ray emission spectra in concert with x-ray diffuse scattering patterns, which provide complementary information to x-ray absorption studies. Key systems presented include a photocatalytic compound.
We design a circularly polarized laser pulse in the infrared frequency and femtosecond time domai... more We design a circularly polarized laser pulse in the infrared frequency and femtosecond time domains, for excitation of the OsH(4) molecule in its first excited pseudorotational state of the triply-degenerate bend. The OsH(4) molecule need not be pre-oriented. After excitation, the central nucleus Os carries out pseudorotation about the axis parallel to the direction of propagation of the laser pulse. This pseudorotation causes a strong electric ring current with a value I=1.53 e fs(-1). The mean value of the radius of the ring current is very small, R=0.0031 a(0), where a(0) is the Bohr radius. According to the Biot-Savart law (|B(R=0)| ~I/R)), this nuclear ring current induces the strongest magnetic field predicted so far in molecules, with a central peak absolute value |B(R=0)| =623 T. To monitor the effect, we propose an IR-pump-X-ray-probe versus an X-ray-probe-only experiment, at the K- and L-edges of X-ray ionization. The results are based on the general quantum theory of excitations of pseudorotations in tetrahedral molecules AB(4), driven by a circularly polarized laser pulse.
We present a novel, highly versatile, and self-referenced arrival time monitor for measuring the ... more We present a novel, highly versatile, and self-referenced arrival time monitor for measuring the femtosecond time delay between a hard X-ray pulse from a free-electron laser and an optical laser pulse, measured directly on the same sample used for pump-probe experiments. Two chirped and picosecond long optical supercontinuum pulses traverse the sample with a mutually fixed time delay of 970 fs, while a femtosecond X-ray pulse arrives at an instant in between both pulses. Behind the sample the supercontinuum pulses are temporally overlapped to yield near-perfect destructive interference in the absence of the X-ray pulse. Stimulation of the sample with an X-ray pulse delivers non-zero contributions at certain optical wavelengths, which serve as a measure of the relative arrival time of the X-ray pulse with an accuracy of better than 25 fs. We find an excellent agreement of our monitor with the existing timing diagnostics at the SACLA XFEL with a Pearson correlation value of 0.98. We d...
The high spin to low spin transition of siderite is studied by simultaneous X-ray emission and X-... more The high spin to low spin transition of siderite is studied by simultaneous X-ray emission and X-ray Raman scattering spectroscopy.
Reaction pathways of biochemical processes are influenced by the dissipative electrostatic intera... more Reaction pathways of biochemical processes are influenced by the dissipative electrostatic interaction of the reagents with solvent water molecules. The simulation of these interactions requires a parametrization of the permanent and induced dipole moments. However, the underlying molecular polarizability of water and its dependence on ions are partially unknown. Here, we apply intense terahertz pulses to liquid water, whose oscillations match the timescale of orientational relaxation. Using a combination of terahertz pump / optical probe experiments, molecular dynamics simulations, and a Langevin dynamics model, we demonstrate a transient orientation of their dipole moments, not possible by optical excitation. The resulting birefringence reveals that the polarizability of water is lower along its dipole moment than the average value perpendicular to it. This anisotropy, also observed in heavy water and alcohols, increases with the concentration of sodium iodide dissolved in water. ...
Page 1. 8 Observing molecular structure changes and dynamics in polar solutionAlexander L. Dobrya... more Page 1. 8 Observing molecular structure changes and dynamics in polar solutionAlexander L. Dobryakov1, Nikolaus P. Ernsting1, Wojciech Gawelda2, Christian Bressler2, Majed Chergui2 1 Department of Chemistry, Humboldt ...
ABSTRACT We present our new results exploiting simultaneously picosecond and femtosecond x-ray em... more ABSTRACT We present our new results exploiting simultaneously picosecond and femtosecond x-ray emission spectra in concert with x-ray diffuse scattering patterns, which provide complementary information to x-ray absorption studies. Key systems presented include a photocatalytic compound.
We design a circularly polarized laser pulse in the infrared frequency and femtosecond time domai... more We design a circularly polarized laser pulse in the infrared frequency and femtosecond time domains, for excitation of the OsH(4) molecule in its first excited pseudorotational state of the triply-degenerate bend. The OsH(4) molecule need not be pre-oriented. After excitation, the central nucleus Os carries out pseudorotation about the axis parallel to the direction of propagation of the laser pulse. This pseudorotation causes a strong electric ring current with a value I=1.53 e fs(-1). The mean value of the radius of the ring current is very small, R=0.0031 a(0), where a(0) is the Bohr radius. According to the Biot-Savart law (|B(R=0)| ~I/R)), this nuclear ring current induces the strongest magnetic field predicted so far in molecules, with a central peak absolute value |B(R=0)| =623 T. To monitor the effect, we propose an IR-pump-X-ray-probe versus an X-ray-probe-only experiment, at the K- and L-edges of X-ray ionization. The results are based on the general quantum theory of excitations of pseudorotations in tetrahedral molecules AB(4), driven by a circularly polarized laser pulse.
We present a novel, highly versatile, and self-referenced arrival time monitor for measuring the ... more We present a novel, highly versatile, and self-referenced arrival time monitor for measuring the femtosecond time delay between a hard X-ray pulse from a free-electron laser and an optical laser pulse, measured directly on the same sample used for pump-probe experiments. Two chirped and picosecond long optical supercontinuum pulses traverse the sample with a mutually fixed time delay of 970 fs, while a femtosecond X-ray pulse arrives at an instant in between both pulses. Behind the sample the supercontinuum pulses are temporally overlapped to yield near-perfect destructive interference in the absence of the X-ray pulse. Stimulation of the sample with an X-ray pulse delivers non-zero contributions at certain optical wavelengths, which serve as a measure of the relative arrival time of the X-ray pulse with an accuracy of better than 25 fs. We find an excellent agreement of our monitor with the existing timing diagnostics at the SACLA XFEL with a Pearson correlation value of 0.98. We d...
The high spin to low spin transition of siderite is studied by simultaneous X-ray emission and X-... more The high spin to low spin transition of siderite is studied by simultaneous X-ray emission and X-ray Raman scattering spectroscopy.
Reaction pathways of biochemical processes are influenced by the dissipative electrostatic intera... more Reaction pathways of biochemical processes are influenced by the dissipative electrostatic interaction of the reagents with solvent water molecules. The simulation of these interactions requires a parametrization of the permanent and induced dipole moments. However, the underlying molecular polarizability of water and its dependence on ions are partially unknown. Here, we apply intense terahertz pulses to liquid water, whose oscillations match the timescale of orientational relaxation. Using a combination of terahertz pump / optical probe experiments, molecular dynamics simulations, and a Langevin dynamics model, we demonstrate a transient orientation of their dipole moments, not possible by optical excitation. The resulting birefringence reveals that the polarizability of water is lower along its dipole moment than the average value perpendicular to it. This anisotropy, also observed in heavy water and alcohols, increases with the concentration of sodium iodide dissolved in water. ...
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