Experimental and Theoretical Study on Electron Momentum Spectroscopy of SF6: Distorted-Wave and Vibrational Motion.

The vibrational and distorted-wave effects are usually invoked to explain the measured electron momentum profiles for molecular orbitals. The vibrational effect can be accounted for quantitatively by a harmonic analytical quantum mechanical approach within the plane-wave impulse approximation (PWIA). On the other hand, quantitative calculation considering the distorted-wave effect was available only recently by a multicenter-three-distorted-wave (MCTDW) method (Phys. Rev. A2022, 105, 042805). Here, we report a joint experimental and theoretical investigation on electron momentum spectroscopy of SF6. The experiments were performed using a high-sensitivity (e, 2e) spectrometer employing non-coplanar symmetric geometry with incident electron energy equal to 1200 eV + binding energy. The experimental electron momentum profiles are compared with theoretical calculations by the MCTDW method at equilibrium geometry and by the PWIA method both at equilibrium geometry and considering vibrational motions. For all the measured orbitals, large discrepancies were observed between the experiments and the PWIA calculations at equilibrium geometry. For the highest occupied molecular orbital 1t1g, the vibrational effect can partly explain the high intensity of the experimental momentum profile at low momenta. For the other orbitals, the influence of the vibrational effect is negligible. On the other hand, the MCTDW calculations improve the agreement with the experiments for all the observed orbitals, indicating that the distorted-wave effect plays an important role in reproducing the measured momentum profiles of SF6.

Fragmentation of SO2 q+ (q = 2-4) induced by 1 keV electron collision.

We report an investigation on the fragmentation dynamics of SO2 q+ (q = 2-4) induced by 1 keV electron collision utilizing an ion momentum imaging spectrometer. Six complete Coulomb explosion channels were observed using the time-of-flight correlation map. The kinetic energy release distributions for these channels were obtained and compared with those available in the literature. The fragmentation mechanisms of the three-body dissociation channels were analyzed by the Dalitz plots and Newton diagrams. Both concerted breakup and sequential fragmentation pathways were identified in the channel SO2 3+ → O+ + O+ + S+, whereas only the concerted breakup mechanism was confirmed for the channels SO2 4+ → O+ + O+ + S2+ and SO2 4+ → O2+ + O+ + S+. Using the Coulomb explosion model, we determined the molecular geometry from the concerted fragmentation channels, and the obtained bond lengths and angles from the higher kinetic energy release peaks are close to that of the neutral SO2 obtained by high-level quantum chemical calculation. The present results indicate that the electron impact experiment is a potential tool for the Coulomb explosion imaging of small molecules.

Pathways of two-body dissociation of BrCNq+ (q = 2, 3) induced by electron collision.

Pathways of two-body fragmentation of BrCNq+ (q = 2, 3) have been explored by combined experimental and theoretical studies. In the experiment, the BrCN molecule is ionized by 1 keV electron impact and the created fragment ions are detected using an ion momentum imaging spectrometer. Six two-body fragmentation channels are identified. By measuring the momentum vectors of the fragment ions, the kinetic energy release (KER) distributions for these channels have been determined. Theoretically, the potential energy curves of BrCNq+ (q = 2, 3) as a function of Br-C and C-N internuclear distances are calculated by the complete active space self-consistent field method. By comparing the measured KER and theoretical predictions, pathways for the fragmentation channels are assigned. The relative branching ratios of the channels are also determined.

Social relationship adjustments within the same sex promote marital bliss.

Parental care is essential for biological systems. Marital bliss is one of the ideal paradigms for parental care, in which males contribute in raising offspring and females require a courtship time. Yet marital bliss state is neither Nash equilibrium nor Pareto optimum for the classic Battle of the Sexes. It thus leads to a gap between evolutionary theory and marital bliss. Previous works concentrate on the pairwise interactions between the two sexes to fill this gap, such as the courtship time and encounter rate. The social relationships within the same sex, however, receives much less attention. Here we investigate how social relationships within the same sex change marital bliss by introducing the coevolution of strategy and social network. Based on the time scale separation, it is found that a symmetric game is emergent via social adjustments within each sex, and the evolutionary outcome is determined by the interplay between the emergent symmetric game and the Battle of the Sexes. We find that marital bliss can be promoted when males are rational (strong selection limit) and females are irrational (weak selection limit); the stable Coy-Coy social relationships both stabilize and speed up marital bliss; the general criterion of stabilizing marital bliss for arbitrary imitation function are found, which are verified by simulations. Furthermore, the emergent symmetric games are insightful for determining whether the stable marital bliss is global stable. Our work provides an alternative avenue to facilitate marital bliss, which can be applied for general asymmetric games on dynamical networks.

[Impacts of ODF2 gene knockdown on the sperm motility and fertility of male mice].

OBJECTIVE: To investigate the knockdown of the outer dense fiber protein 2 (ODF2) gene on the sperm motility and fertility of male mice. METHODS: We constructed three knockdown vectors with the target gene ODF2 and one control vector without the target gene. After infecting ICR mice, we determined the vector with the best knockdown effect by RT-PCR and Western blot and reinfected the mice with it. Then we obtained and analyzed the sperm motility parameters, pathological changes of the testis issue, and the litter size of the mice with gene knockdown. RESULTS: Compared with the normal controls, the mice infected with the vector with the best knockdown effect showed significantly decreased sperm motility parameters, pathomorphological abnormalities of the testis, and a reduced litter size (10.86 ± 1.28 vs 12.72 ± 2.05, P = 0.001). CONCLUSION: Decreased expression of the ODF2 gene deceases sperm motility parameters, impairs the morphology of the testis and affects the fertility of male mice.

Electron Momentum Spectroscopy Study on the Valence Electronic Structure of Dimethyl Sulfide Considering Vibrational Effects.

We report an electron momentum spectroscopy study on the valence electronic structure of dimethyl sulfide. The binding energy and electron momentum profiles are measured using a high-sensitivity (e, 2e) apparatus employing a symmetric non-coplanar geometry at an incident energy of 1200 eV plus binding energy. The measurements are compared with the theoretical calculations by density functional theory performed both at equilibrium molecular geometry and by considering vibrational effects through a harmonic analytical quantum mechanical approach. The results demonstrate a significant influence of nuclear vibrational motions on the momentum profiles for valence orbitals of dimethyl sulfide, especially for 5b2, 1a2, and 4b2. A detailed analysis shows that the observed vibrational effects come mainly from vibrational normal modes breaking the mirror symmetry of (CH3)2S with respect to a plane perpendicular to the O-S-O plane.

Ultrafast Proton Transfer Dynamics on the Repulsive Potential of the Ethanol Dication: Roaming-Mediated Isomerization versus Coulomb Explosion.

If a molecular dication is produced on a repulsive potential energy surface (PES), it normally dissociates. Before that, however, ultrafast nuclear dynamics can change the PES and significantly influence the fragmentation pathway. Here, we investigate the electron-impact-induced double ionization and subsequent fragmentation processes of the ethanol molecule using multiparticle coincident momentum spectroscopy and ab initio dynamical simulations. For the electronic ground state of the ethanol dication, we observe several fragmentation channels that cannot be reached by direct Coulomb explosion (CE) but require preceding isomerization. Our simulations show that ultrafast hydrogen or proton transfer (PT) can stabilize the repulsive PES of the dication before the direct CE and form intermediate H2 or H2O. These neutrals stay in the vicinity of the precursor, and roaming mechanisms lead to isomerization and finally PT resulting in emission of H3+ or H3O+. The present findings can help to understand the complex fragmentation dynamics of molecular cations.

Fragmentation dynamics of nitrogen trifluoride induced by electron collision.

The fragmentation dynamics of nitrogen trifluoride (NF3) in collisions with a 500 eV electron is studied by using a momentum imaging spectrometer. The kinetic energy releases of two-body, three-body, and four-body fragmentation channels of NF3 q+ (q = 2, 3) are investigated. The fragmentation dynamics of three-body, as well as four-body, dissociation channels is analyzed by the Dalitz plot and the Newton diagram. It is found that for all of the dissociation channels, the fragment including N atom (ion) always shares significant momenta, regardless of whether it is charged. For F atom, however, it is always emitted with negligible momenta.

Fragmentation dynamics of CS2 in collisions with 1.0 keV electrons.

The dissociation dynamics of CS2 molecules in collisions with 1.0 keV electrons is studied. We observe a series of two- and three-body fragmentation channels which are identified from the correlation map between fragment ions. For all of the channels, the kinetic energy release (KER) distributions are obtained. The Dalitz plot and Newton diagram are adopted to analyze the fragmentation dynamics of the three-body dissociation channels. For C S 2 3 + and C S 2 4 + , both the concerted and sequential fragmentation mechanisms are observed where the concerted mechanism dominates. For C S 2 5 + , only the concerted mechanism is observed. Two types of Coulomb explosion models considering the molecular vibration are adopted to simulate the experimental KER distributions of the three-body channels. While obvious deviations are observed considering each ion during the whole dissociation process with an integer charge, good agreement can be achieved within deviation less than 5% if the charge state of the ions are adopted from ab initio calculations.

Electron Momentum Spectroscopy Investigation of Molecular Conformations of Ethanol Considering Vibrational Effects.

The interpretation of experimental electron momentum distributions (EMDs) of ethanol, one of the simplest molecules having conformers, has confused researchers for years. High-level calculations of Dyson orbital EMDs by thermally averaging the gauche and trans conformers as well as molecular dynamical simulations failed to quantitatively reproduce the experiments for some of the outer valence orbitals. In this work, the valence shell electron binding energy spectrum and EMDs of ethanol are revisited by the high-sensitivity electron momentum spectrometer employing symmetric noncoplanar geometry at an incident energy of 1200 eV plus binding energy, together with a detailed analysis of the influence of vibrational motions on the EMDs for the two conformers employing a harmonic analytical quantum mechanical (HAQM) approach by taking into account all of the vibrational modes. The significant discrepancies between theories and experiments in previous works have now been interpreted quantitatively, indicating that the vibrational effect plays a significant role in reproducing the experimental results, not only through the low-frequency OH and CH3 torsion modes but also through other high-frequency ones. Rational explanation of experimental momentum profiles provides solid evidence that the trans conformer is slightly more stable than the gauche conformer, in accordance with thermodynamic predictions and other experiments. The case of ethanol demonstrates the significance of considering vibrational effects when performing a conformational study on flexible molecules using electron momentum spectroscopy.

[Expressions of ODF2 mRNA and protein are down-regulated in the sperm of asthenospermia patients].

OBJECTIVE: To investigate the mRNA and protein expressions of outer dense fiber 2 (ODF2) in the sperm of the asthenospermia patient and their differences from those in normal healthy men. METHODS: According to the WHO criteria, we collected semen samples from 45 asthenozoospermia patients and 15 normal healthy volunteers. Using computer-assisted sperm analysis (CASA), we divided the semen samples from the asthenospermia patients into a mild, a moderate and a severe group, and determined the mRNA and protein expressions of ODF2 in different groups by RT-PCR and Western blot. RESULTS: Compared with the normal healthy men, the expression of the ODF2 gene showed no statistically significant difference in the mild asthenospermia group (1.112 0 ± 0.525 5 vs 0.688 0 ± 0.372 0, P >0.05) but remarkably decreased in the moderate (0.483 3 ± 0.186 3, P <0.05) and severe asthenospermia patients (0.448 3 ± 0.340 8, P <0.01). The OD value (ODF2/ß-actin) of the ODF2 protein in the normal men exhibited no statistically significant difference from that in the mild asthenospermia group (0.458 7 ± 0.052 1 vs 0.326 1 ± 0.071 4, P >0.05), but markedly lower than in the moderate (0.145 4 ± 0.053 6, P <0.05) and severe asthenospermia patients (0.122 7 ± 0.045 7, P <0.01), which was consistent with the results of RT-PCR. CONCLUSIONS: Decreased mRNA and protein expressions of ODF2 in the sperm are positively correlated with declined sperm motility of the asthenospermia patient, which is suggestive of the involvement of the ODF2 gene in the regulation of sperm motility.

Vibrational Effects on Electron Momentum Distributions of Outer-Valence Orbitals of Oxetane.

Vibrational effects on electron momentum distributions (EMDs) of outer-valence orbitals of oxetane are computed with a comprehensive consideration of all vibrational modes. It is found that vibrational motions influence EMDs of all outer-valence orbitals noticeably. The agreement between theoretical and experimental momentum profiles of the first five orbitals is greatly improved when including molecular vibrations in the calculation. In particular, the large turn-up at low momentum in the experimental momentum profile of the 3b1 orbital is well interpreted by vibrational effects, indicating that, besides the low-frequency ring-puckering mode, C-H stretching motion also plays a significant role in affecting EMDs of outer-valence orbitals of oxetane. The case of oxetane exhibits the significance of checking vibrational effects when performing electron momentum spectroscopy measurements.

Fragmentation dynamics of carbonyl sulfide in collision with 500 eV electron.

The fragmentation dynamics of OCSq+ (q = 2, 3, 4) induced by electron collision at an impact energy of 500 eV is studied. By using the momentum imaging technique, the three dimensional momentum vectors of all the fragments are obtained, which enables us to analyse both the kinetic energy release and the momentum correlations for a certain fragmentation channel. Up to fifteen dissociation channels are analyzed including six, five, and four channels for two-body, and incomplete and complete three-body Coulomb fragmentations. For three-body dissociation, the fragmentation mechanisms are investigated with the help of Dalitz plot and Newton diagram. It is found that the sequential fragmentation involves in OCS2+→O+C++S+ with S+ emitted first and in OCS3+→O++C++S+ with O-C and C-S bonds breaking first. The remaining channels, however, always dissociate through a concerted mechanism. The relative intensities of the channels are also presented in this work.

Observation of the interference effect in vibrationally resolved electron momentum spectroscopy of H2.

We report the first measurement on vibrationally resolved electron momentum spectroscopy of H2 by using a high-resolution (e, 2e) spectrometer. The vibrational-specific experimental momentum profiles have been obtained and shown to be in agreement with calculations of (e, 2e) ionization cross sections taking into account the vibrational wave functions. Distinct deviations from Franck-Condon predictions have been observed in vibrational ratios of cross sections, which can readily be ascribed to the Young-type two-center interference. Unlike previous (e, 2e) work, the present observation of an interference effect does not rely on the comparison with the one-center atomic cross section.

Ring-puckering effects on electron momentum distributions of valence orbitals of oxetane.

The binding energy spectra and electron momentum distributions for the outer-valence molecular orbitals of oxetane have been measured utilizing (e, 2e) electron momentum spectrometer with non-coplanar asymmetric geometry at the impact energy of 2500 eV. The experimental momentum distributions were compared with the density functional theory calculations employing B3LYP hybrid functional with aug-cc-pVTZ basis set. It was found that the calculation at planar geometry (C2v) completely fails to interpret the large "turn-up" at low momentum region in electron momentum distribution of the highest occupied molecular orbital (HOMO) 3b1, while the calculations considering the thermal abundances of planar (C2v) and bent (Cs) conformers or the thermally populated vibrational states of ring-puckering motion have significantly improved the agreement. The results indicate that the ring-puckering motion of oxetane has a strong effect on the electron density distribution of HOMO.

Experimental and theoretical investigation on the outer valence electronic structure of cyclopropylamine by (e, 2e) electron momentum spectroscopy.

The binding energy spectra and electron momentum distributions for the outer-valence molecular orbitals of gaseous cyclopropylamine (CPA) have been measured by (e, 2e) electron momentum spectrometer employing noncoplanar asymmetric geometry at the impact energy of 2500 eV. The experimental results are interpreted on the basis of the quantitative calculations of the ionization energies and the relevant molecular orbitals at benchmark theoretical levels using the outer-valence Green's function method, the symmetry-adapted cluster configuration interaction method, and the density functional theory with B3LYP hybrid functional. The total energies of the trans and gauche conformers of CPA are also calculated by the second-order Møller-Plesset perturbation theory with large basis sets and the derived enthalpy differences (2.02-2.12 kcal/mol) are consistent with the previous experimental data (2.19 kcal/mol). The theoretical binding energy spectra and electron momentum distributions, in which the relative abundances of trans and gauche are taken into account, are generally in accordance with the experimental results except for the ionization band from the trans 8a' and gauche 11a orbitals. The discrepancy is explained qualitatively in view of the picture of molecular geometry change at the instant of ionization.

Three-dimensional reconstructions of mechanosensory end organs suggest a unifying mechanism underlying dynamic, light touch.

Specialized mechanosensory end organs within mammalian skin-hair follicle-associated lanceolate complexes, Meissner corpuscles, and Pacinian corpuscles-enable our perception of light, dynamic touch 1 . In each of these end organs, fast-conducting mechanically sensitive neurons, called Aß low-threshold mechanoreceptors (Aß LTMRs), associate with resident glial cells, known as terminal Schwann cells (TSCs) or lamellar cells, to form complex axon ending structures. Lanceolate-forming and corpuscle-innervating Aß LTMRs share a low threshold for mechanical activation, a rapidly adapting (RA) response to force indentation, and high sensitivity to dynamic stimuli 1-6 . How mechanical stimuli lead to activation of the requisite mechanotransduction channel Piezo2 7-15 and Aß RA-LTMR excitation across the morphologically dissimilar mechanosensory end organ structures is not understood. Here, we report the precise subcellular distribution of Piezo2 and high-resolution, isotropic 3D reconstructions of all three end organs formed by Aß RA-LTMRs determined by large volume enhanced Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) imaging. We found that within each end organ, Piezo2 is enriched along the sensory axon membrane and is minimally or not expressed in TSCs and lamellar cells. We also observed a large number of small cytoplasmic protrusions enriched along the Aß RA-LTMR axon terminals associated with hair follicles, Meissner corpuscles, and Pacinian corpuscles. These axon protrusions reside within close proximity to axonal Piezo2, occasionally contain the channel, and often form adherens junctions with nearby non-neuronal cells. Our findings support a unified model for Aß RA-LTMR activation in which axon protrusions anchor Aß RA-LTMR axon terminals to specialized end organ cells, enabling mechanical stimuli to stretch the axon in hundreds to thousands of sites across an individual end organ and leading to activation of proximal Piezo2 channels and excitation of the neuron.