We introduce and demonstrate a new approach to measuring coherent electron wave packets using high-harmonic spectroscopy. By preparing a molecule in a coherent superposition of electronic states, we show that electronic coherence opens previously unobserved high-harmonic-generation channels that connect distinct but coherently related electronic states. Performing the measurements in dynamically aligned nitric oxide (NO) molecules we observe the complex temporal evolution of the electronic coherence under coupling to nuclear motion. Choosing a weakly allowed transition to prepare the wave packet, we demonstrate an unprecedented sensitivity that arises from optical interference between coherent and incoherent pathways. This mechanism converts a 0.1 % excitation fraction into a ∼20 % signal modulation.Measuring the motion of valence-shell electrons in molecules is one of the central goals of modern ultrafast science. The last decade has witnessed very fundamental progress in this area with the development of attosecond streaking [1,2] and interferometric techniques [3] to time resolve electronic dynamics as well as transient absorption [4,5] and strong-field ionization [6-9] to probe electronic wave packets in atomic ions. All of these experiments have been performed on highly-excited states, in the continuum or in ionic species. Electronic dynamics involving the ground state and a low-lying electronically excited state of a neutral molecule have not been observed to date.Here, we introduce a new all-optical technique that allows the measurement of an electronic wave packet in the valence shell of a neutral molecule for the first time. In our pump-probe experiment, an electronic wave packet is created through stimulated Raman scattering and probed by the generation of high-order harmonics (orders 9 to 23) of an infrared laser pulse. Figure 1A illustrates the concept of our measurement. High-harmonic emission from a coherent superposition of two electronic states can be described as a superposition of radiation produced in four channels illustrated by arrows in Fig. 1A. Ionization from and recombination to the same electronic state gives rise to two channels (blue arrows) that are independent of the electronic coherence. Ionization from one state and recombination to the other state gives rise to two additional channels (red arrows) that only contribute to an observable high-harmonic signal if the two states are coherently related. These channels are the key to probing electronic coherence and have not been observed previously.The two channels connecting the same initial and final states (blue arrows) emit radiation that is insensitive to the quantum phase of the initial state. The amplitude of the radiation generated in each of these channels is proportional to the population in each state. These pathways have been exploited to time resolve photochemical dynamics [10,11]. In contrast, the two cross-channels (red arrows) read out the relative quantum phases and encode their difference in the phase of the emitted ra...

Cadmium (Cd) is an environmental pollutant known to cause liver damage; however, the mechanisms of its hepatotoxicity remain poorly understood. In this study, the effects of subchronic exposure in mice to low doses of Cd on energy metabolism and the gut microbiome were evaluated. The exposure of mice to 10 mg/L Cd supplied in drinking water for 10 weeks increased hepatic triacylglycerol (TG), serum free fatty acid (FFA), and TG levels. The mRNA levels of several key genes involved in both de novo FFA synthesis and transport pathways and in TG synthesis in the liver also increased significantly in the Cd-treated mice, indicating that alterations of these genes may be a possible mechanism to explain subchronic Cd exposure induced hepatic toxicity at a molecular level. As for the gut microbiome, at the phylum level, the amounts of Firmicutes and γ-proteobacteria decreased significantly in the feces after 4 weeks of Cd exposure, and the quantity of Firmicutes decreased significantly in the cecum contents after 10 weeks of Cd exposure. In addition, 16S rRNA gene sequencing further revealed that Cd exposure significantly perturbed the gut microflora structure and richness at family and genus levels. The alteration of gut microbiome composition might result in an increase in serum lipopolysaccharide (LPS) and induce hepatic inflammation, which may indirectly cause perturbations of energy homeostasis after Cd exposure. Taken together, the present study indicated that subchronic Cd exposure caused the dysregulation of energy metabolism and changed the gut microbiome composition in mice.

Hot, dense plasmas exhibit screened Coulomb interactions, resulting from the collective effects of correlated many-particle interactions. In the lowest particle correlation order (pair-wise correlations), the interaction between charged plasma particles reduces to the Debye-Hückel (Yukawa-type) potential, characterized by the Debye screening length D. Due to the importance of Coulomb interaction screening in dense laboratory and astrophysical plasmas, hundreds of theoretical investigations have been carried out in the past few decades on the plasma screening effects on the electronic structure of atoms and their collision processes employing the Debye-Hückel screening model. The present article aims at providing a comprehensive review of the recent studies in atomic physics in Debye plasmas. Specifically, the work on atomic electronic structure, photon excitation and ionization, electron/positron impact excitation and ionization, and excitation, ionization and charge transfer of ion-atom/ion collisions will be reviewed.