To date X-ray spectroscopy has become a routine tool that can reveal highly local and element-specific information on the electronic structure of atoms in complex environments. Here, we focus on nuclear dynamical effects in X-ray spectra and develop a rigorous time-correlation method employing ground state molecular dynamics simulations. The importance of nuclear correlation phenomena is demonstrated by comparison against the results from the conventional sampling approach for gas phase water. In contrast to the first-order absorption, second-order resonant inelastic scattering spectra exhibit pronounced fingerprints of nuclear motions. The developed methodology does not depend on the accompanying electronic structure method in principle as well as on the spectral range and, thus, can be applied to, e.g., UV and X-ray photo-electron and Auger spectroscopies.
Modern X-ray spectroscopy has proven itself as a robust tool for probing the electronic structure of atoms in complex environments. Despite working on energy scales that are much larger than those corresponding to nuclear motions, taking nuclear dynamics and the associated nuclear correlations into account may be of importance for X-ray spectroscopy. Recently, we have developed an efficient protocol to account for nuclear dynamics in X-ray absorption and resonant inelastic X-ray scattering spectra [Karsten \textit{et al.} arXiv:1608.03436], based on ground state molecular dynamics accompanied …
Extensions and improvements of empirical force fields are discussed in view of applications to computational vibrational spectroscopy and reactive molecular dynamics simulations. Particular focus is on quantitative studies which make contact with experiments and provide complementary information for a molecular-level understanding of processes in the gas phase and in solution. Methods range from including multipolar charge distributions to reproducing kernel Hilbert space approaches and machine learned energy functions based on neural networks.
The weak interaction does not conserve parity and therefore induces energy shifts in chiral enantiomers that should in principle be detectable in molecular spectra. Unfortunately, the magnitude of the expected shifts are small and in spectra of a mixture of enantiomers, the energy shifts are not resolvable. We propose a nuclear magnetic resonance (NMR) experiment in which we titrate the chirality (enantiomeric excess) of a solvent and measure the diasteriomeric splitting in the spectra of a chiral solute in order to search for an anomalous offset due to parity nonconservation (PNC). We present…
Application of SAP-X2C to Spectroscopy and Comparison to Screened Nuclear Spin-Orbit Approximations
Karlsruhe Institute of Technology (KIT)（卡尔斯鲁厄理工学院）；Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT)（卡尔斯鲁厄理工学院纳米技术研究所）；Institute of Quantum Materials and Technologies, Karlsruhe Institute of Technology (KIT)（卡尔斯鲁厄理工学院量子材料与技术研究所）
We present single- and multiple-quantum correlation $J$-spectroscopy detected in zero ($<\!\!1$~$μ$G) magnetic field using a \Rb vapor-cell magnetometer. At zero field the spectrum of ethanol appears as a mixture of \carbon isotopomers, and correlation spectroscopy is useful in separating the two composite spectra. We also identify and observe the zero-field equivalent of a double-quantum transition in ${}^{13}$C$_2$-acetic acid, and show that such transitions are of use in spectral assignment. Two-dimensional spectroscopy further improves the high resolution attained in zero-field NMR since s…
Here we demonstrate that a term in the nuclear spin Hamiltonian, the antisymmetric \textit{J}-coupling, is fundamentally connected to molecular chirality. We propose and simulate a nuclear magnetic resonance (NMR) experiment to observe this interaction and differentiate between enantiomers without adding any additional chiral agent to the sample. The antisymmetric \textit{J}-coupling may be observed in the presence of molecular orientation by an external electric field. The opposite parity of the antisymmetric coupling tensor and the molecular electric dipole moment yields a sign change of the…
Understanding the reactivity and spectroscopy of aqueous solutions at the atomistic level is crucial for the elucidation and design of chemical processes. However, the simulation of these systems requires addressing the formidable challenges of treating the quantum nature of both the electrons and nuclei. Exploiting our recently developed methods that provide acceleration by up to two orders of magnitude, we combine path integral simulations with on-the-fly evaluation of the electronic structure at the hybrid density functional theory level to capture the interplay between nuclear quantum effe…
We consider optical spectroscopy of molecular junctions from the quantum transport perspective when radiation field is quantized and optical response of the system is simulated as photon flux. Using exact expressions for photon and electronic fluxes derived within the nonequilibrium Green function (NEGF) methodology and utilizing fourth order diagrammatic perturbation theory in molecular coupling to radiation field we perform simulations employing realistic parameters. Results of the simulations are compared to the bare perturbation theory (PT) usually employed in studies on nonlinear optical …
Owing to their high surface area, their high stability, and their hydrophobicity, periodic mesoporous organosilica (PMO) materials represent promising catalytic support for environmentally friendly chemical processes in water. We investigate here how the calcination of PMO material with benzene linkers (PMOB) allows its functionalization. Conventional and dynamic nuclear polarization (DNP)-enhanced NMR spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy, and X-ray photoelectron spectroscopy prove that calcination at 450 °C results in the oxidation of phenylene bridges int…
Zero- to ultralow-field nuclear magnetic resonance (ZULF NMR) is an alternative spectroscopic method to high-field NMR, in which samples are studied in the absence of a large magnetic field. Unfortunately, there is a large barrier to entry for many groups, because operating the optical magnetometers needed for signal detection requires some expertise in atomic physics and optics. Commercially available magnetometers offer a solution to this problem. Here we describe a simple ZULF NMR configuration employing commercial magnetometers, and demonstrate sufficient functionality to measure samples w…
The error-robust and short composite operations named ConCatenated Composite Pulses (CCCPs), developed as high-precision unitary operations in quantum information processing (QIP), are derived from composite pulses widely employed in nuclear magnetic resonance (NMR). CCCPs simultaneously compensate for two types of systematic errors, which was not possible with the known composite pulses in NMR. Our experiments demonstrate that CCCPs are powerful and versatile tools not only in QIP but also in NMR.
Rotational transitions of $iso$-propyl cyanide, (CH$_3$)$_2$CHCN, also known as $iso$-butyronitrile, were recorded using long-path absorption spectroscopy in selected regions between 37 and 600 GHz. Further measurements were carried out between 6 and 20 GHz employing Fourier transform microwave (FTMW) spectroscopy on a pulsed molecular supersonic jet. The observed transitions reach $J$ and $K_a$ quantum numbers of 103 and 59, respectively, and yield accurate rotational constants as well as distortion parameters up to eighth order. The $^{14}$N nuclear hyperfine splitting was resolved in partic…
Raman spectroscopy of crystalline/molecular systems is well backed with quantum chemical calculations and group theory, making it a unique characterization tool. For the "intermediate" case of nanoscale systems, however, the use of Raman spectroscopy is limited by the lack of such theoretical bases. Here, we suggest to couple a scaled quantum-mechanical (SQM) calculation with the phonon confinement model (PCM) to construct a universal and physically consistent basis for nanoscale Raman spectroscopy. Unlike the commonly used one-dimensional dispersion PCM, we take into account the confinement a…
Microfluidic NMR spectroscopy can probe chemical and bio-chemical processes non-invasively in a tightly controlled environment. We present a dual-channel modular probe assembly for high efficiency microfluidic NMR spectroscopy and imaging. It is compatible with a wide range of microfluidic devices, without constraining the fluidic design. It collects NMR signals from a designated sample volume on the device with high sensitivity and resolution. Modular design allows adapting the detector geometry to different experimental conditions with minimal cost, by using the same probe base. The complete…
Quantum sensors based on nitrogen-vacancy centers in diamond have emerged as a promising detection modality for nuclear magnetic resonance (NMR) spectroscopy owing to their micron-scale detection volume and non-inductive based detection. A remaining challenge is to realize sufficiently high spectral resolution and concentration sensitivity for multidimensional NMR analysis of picoliter sample volumes. Here, we address this challenge by spatially separating the polarization and detection phases of the experiment in a microfluidic platform. We realize a spectral resolution of 0.65 +/- 0.05 Hz, a…
Nuclear moments, charge radii, and magnetization distribution parameters of Ag isotopes from laser spectroscopy and \textit{ab initio} electronic-structure calculations
Petersburg Nuclear Physics Institute named by B.P. Konstantinov of National Research Centre “Kurchatov Institute”（以B.P.康斯坦丁诺夫命名的国家研究中心“库尔恰托夫研究所”圣彼得堡核物理研究所）；Saint Petersburg State University（圣彼得堡国立大学）；KU Leuven, Instituut voor Kern- en Stralingsfysica（荷语鲁汶大学核与辐射物理研究所）；Centre for Cold Matter, Imperial College London（伦敦帝国理工学院冷物质中心）；State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University（清华大学物理系低维量子物理国家重点实验室）
We demonstrate nuclear magnetic resonance (NMR) spectroscopy of picoliter-volume solutions with a nanostructured diamond chip. Using optical interferometric lithography, diamond surfaces were nanostructured with dense, high-aspect-ratio nanogratings, enhancing the surface area by more than a factor of 15 over mm^2 regions of the chip. The nanograting sidewalls were doped with nitrogen-vacancy (NV) centers so that more than 10 million NV centers in a (25 micrometer)^2 laser spot are located close enough to the diamond surface (5 nm) to detect the NMR spectrum of 1 pL of fluid lying within adjac…
