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Light–matter interactions are usually described within the electric-dipole approximation, where the magnetic-field component and the spatial variation of the light electric field over the relevant electronic length scales are both ignored. Non-dipole effects in photoionization were revealed to be tiny from the infrared to the soft X-ray domains, and all non-dipole observations reported so far were limited to single-pulse, single-colour measurements. Here we advance attosecond time-resolved spectroscopy into the non-dipole interaction regime. Using a self-referenced attosecond photoelectron interferometry on helium atoms, we resolve the electron subcycle motion along the light propagation direction in the 15 pm range driven by the magnetic component of a near-infrared laser field. Furthermore, we measure a time delay of 15 ± 10 as between the electric-dipole and electric-quadrupole transitions by resolving the asymmetry of the photoelectron forward–backward yields with attosecond resolution. These fundamental findings are supported by ab initio calculations based on the non-dipole time-dependent Schrödinger equation.

Due to its strong ultraviolet absorption, low background interference in the small molecular range, and salt tolerance capacity, N-phenyl-2-naphthylamine (PNA) was developed as a novel matrix in the present study for analysis and imaging of small molecules by matrix-assisted laser desorption/ionization mass spectrometry time-of-fight (MALDI-TOF MS). The newly developed matrix displayed good performance in analysis of a wide range of small-molecule metabolites including free fatty acids, amino acids, peptides, antioxidants, and phospholipids. In addition, PNA-assisted LDI MS imaging of small molecules in brain tissue of rats subjected to middle cerebral artery occlusion (MCAO) revealed unique distributions and changes of 89 small-molecule metabolites including amino acids, antioxidants, free fatty acids, phospholipids, and sphingolipids in brain tissue 24 h postsurgery. Fifty-nine of the altered metabolites were identified, and all the changed metabolites were subject to relative quantitation and statistical analysis. The newly developed matrix has great potential application in the field of biomedical research.

We report on the scaling of the photoelectron holography with the laser ellipticity in strong-field atomic ionization. We find that the spacing of the holographic fringe gradually decreases with increasing of the ellipticity. In terms of the strong-field approximation, the scaling of the fringe spacing with the laser ellipticity is explained by the effect of the initial transverse momenta at the tunnel exit. With increasing of the laser ellipticity, a ridge structure arising from forward scattering electrons is observed in the low-energy region of the electron momentum distribution. An analytic formula is obtained that demarcates the phase diagram for the observation of the holographic pattern and ridge structure in elliptically polarized laser fields.

Polyhydroxylated alkaloids, or alkaloidal iminosugars, which exhibit potent bioactivity as glycosidase inhibitors, can be used as potential therapeutic agents or as tools for probing into biological recognition processes. Mulberry has aroused considerable research interest in recent decades as it is rich in polyhydroxylated alkaloids, in particular it is a major natural source of 1-deoxyjirimycin (DNJ). In the present work, we achieved the rapid and direct detection of polyhydroxylated alkaloids in mulberry using leaf spray mass spectrometry. By semi-quantitative analysis, the relative content of DNJ in different plant materials from mulberry trees was recorded and the experimental results provided us an insight into the distribution of DNJ in mulberry, which can be instructive and informative for the practical production of functional or medical mulberry food. In addition, thanks to its fast, simple and high throughput characteristics, the leaf spray method exhibits promising application in the rapid screening of lead compounds from natural plants during drug development.

We have investigated the diffraction spectra of photoelectrons from one-photon single ionization of diatomic molecules by ultrashort extreme ultraviolet pulses. The result shows that the diffraction patterns strongly depend on the internuclear distances of molecules. With these diffraction patterns, we succeed in measuring the transient internuclear distances of small-distance molecules with a high precision. This provides a simple and efficient method for imaging molecular transient structures, avoiding the complicated recovering process of the diffraction pattern in the imaging with rescattered electrons.

Auf das Anion ist Verlass: Der Austausch des Anions einer Indium‐Lewis‐Säure bewirkt einen bemerkenswerten Regioselektivitätswechsel bei asymmetrischen 1,2‐ und 1,4‐Additionen. N‐geschützte Indole und β,γ‐ungesättigte α‐Ketoester lieferten die Addukte mit ausgezeichneter Enantioselektivität (siehe Schema).

You can count on the anion: Simply swapping the anions of an indium Lewis acid leads to a remarkable regioselectivity switch between asymmetric 1,2‐ and 1,4‐addition reactions. N‐protected indoles and β,γ‐unsaturated α‐keto esters gave adducts with excellent enantioselectivity (see scheme).

Herbicides such as atrazine are widely used in the biosphere. Urine analysis is usually performed to evaluate the toxicological effects associated with atrazine exposure. A simple procedure based on the extractive electrospray ionization mass spectrometry (EESI-MS) method was established to detect atrazine and its metabolites in undiluted raw urine without sample pretreatment. A 4.3 × 10−14g atrazine in spiked raw urine was detected and identified by EESI/MS/MS/MS. The detection limit was found to be 0.4 fg for atrazine (m/z 174) and 0.2 fg for 2-chloro-4, 6-diamino-S-triazine (DACT) (m/z 129) (S/N = 3) in EESI/MS/MS. A linear dynamic range of 4–5 orders of magnitude (r = 0.996) was determined for both atrazine and DACT. A single sample analysis was completed using tandem EESI-MS/MS within 1 min, providing a practical convenient method for rapid analysis of trace amounts of targeted metabolites present in complex matrices. Thus, tandem EESI-MS is potentially useful for previously discovered biomarker detection in multiple applications such as clinical diagnosis, drug discovery and forensic science.

Strong-field tunneling ionization is the first step for a broad class of phenomena in intense laser-atom/molecule interactions. Accurate information about the electron wave packet from strong-field tunneling ionization of atoms and molecules is of essential importance for understanding various tunneling ionization triggered processes. Here, we survey the property of the electron wave packet in tunneling ionization of molecules with a method based on strong-field photoelectron holography. By solving the time-dependent Schrödinger equation, it is shown that the holographic interference in the photoelectron momentum distribution exhibits the asymmetric behavior with respect to the laser polarization direction, when the molecule is aligned with a nonzero angle to the linearly polarized laser field. We demonstrate that this asymmetry is due to the nonzero initial transverse displacement of the electron wave packet at tunneling. By analyzing the holographic interference, this transverse displacement for the launching of electron wave packet tunneling from the molecules is accurately retrieved. This displacement is directly related to the electron density distribution in molecules, and thus our work developed a novel concept for probing electronic structure in molecules.

Ionization of molecules by strong laser fields launches an electron wave packet. This electron wave packet, which can be driven back by the field to recollide with the parent ion, has been widely explored to probe the ultrafast nuclear dynamics. We numerically demonstrate the precise control of the temporal characteristic of the recolliding electron wave packet (REWP) by orthogonally polarized two-color fields. Through changing the relative phase of the two fields, the revisit time of REWP can be manipulated with a resolution of less than 200?attos, thus significantly improving the resolution of the well known molecular clock. This provides an efficient method for real-time observation of the ultrafast molecular dynamics with attosecond resolution.

Electromagnetic stirring (EMS) is an efficient technology to control the flow structure in slab continuous casting mold. But there is still an important opened problem to be answered firstly, that is, what kind of flow structure is our goal by using electromagnetic stirring in order to get good casting products, and how to optimize the flow fields in slab continuous casting mold with EMS? Two kinds of research paradigms are proposed in this study. One is based on causal relationship between the flow field and its effects on the mold flux entrapment and solidification process. Two parameters, named Mold Flux Entrapment Index and Velocity Uniform Index were proposed in order to evaluate the flow field in the mold. Based on these two indexes, optimization stirring parameters were proposed under different casting situation. The other research paradigm is machine learning big data model based on correlation analysis of nearly all the input parameters of casting machine and slab quality as an output parameter. Data acquisition from the continuous casting machine, data mining by machine learning algorithms and online automatic control parameters output are three main aspects in the second research frame.

Using the classical-trajectory Monte Carlo model, we have theoretically studied the angular momentum distribution of frustrated tunneling ionization (FTI) of atoms in strong laser fields. Our results show that the angular momentum distribution of the FTI events exhibits a double-hump structure. With this classical model, we back traced the tunneling coordinates, i.e., the tunneling time and initial transverse momentum at tunneling ionization. It is shown that for the events tunneling ionized at the rising edge of the electric field, the final angular momentum exhibits a strong dependence on the initial transverse momentum at tunneling. While for the events ionized at the falling edge, there is a relatively harder recollision between the returning electron and the parent ion, leading to the angular momentum losing the correlation with the initial transverse momentum. Our study suggests that the angular momentum of the FTI events could be manipulated by controlling the initial coordinates of the tunneling ionization.

Swapping the anions of an indium Lewis acid leads to a remarkable regioselectivity switch between asymmetric 1,2‐ and 1,4‐addition reactions of N‐protected indoles (II) and β,γ‐unsaturated α‐keto esters (III).