Ramsey interferometry through coherent X2Σg+−A2Πu−B2Σu+X^2\Sigma_g^+ - A^2\Pi_u - B^2\Sigma_u^+ coupling and population transfer in N2+^+_2 air laser

The laser-like coherent emission at 391nm from N$_2$ gas irradiated by strong 800nm pump laser and weak 400nm seed laser is theoretically investigated. Recent experimental observations are well simulated, including temporal profile, optical gain and periodic modulation of the 391nm signal from N$_2^+$. Our calculation sheds light on the long standing controversy on whether population inversion is indispensable for the optical gain. We demonstrate the Ramsey interference fringes of the emission intensity at 391nm formed by additionally injecting another 800nm pump or 400nm seed, which are well explained by the coherent modulation of transition dipole moment and population between the $A^2\Pi_u(\nu=2)$-$X^2\Sigma_g^+$ states as well as the $B^2\Sigma_u^+ (\nu=0)$-$X^2\Sigma_g^+$ states. This study provides versatile possibilities for the coherent control of $\text{N}_2^+$ air laser.Comment: 5 pages, 5 figure

Quantum state tomography of molecules by ultrafast diffraction

Ultrafast electron diffraction and time-resolved serial crystallography are the basis of the ongoing revolution in capturing at the atomic level of detail the structural dynamics of molecules. However, most experiments capture only the probability density of the nuclear wavepackets to determine the time-dependent molecular structures, while the full quantum state has not been accessed. Here, we introduce a framework for the preparation and ultrafast coherent diffraction from rotational wave packets of molecules, and we establish a new variant of quantum state tomography for ultrafast electron diffraction to characterize the molecular quantum states. The ability to reconstruct the density matrix, which encodes the amplitude and phase of the wavepacket, for molecules of arbitrary degrees of freedom, will enable the reconstruction of a quantum molecular movie from experimental x-ray or electron diffraction data

Negotiating scholarly identity through an international doctoral workshop: A cosmopolitan approach to doctoral education

Current trends in the internationalization of doctoral programs require new understandings of the formation of scholarly identity. This study explores the utility of a cosmopolitan perspective. It reports on identity projects sparked by Chinese students’ participation in a doctoral workshop in Australia; it highlights the realization, retrieval, repositioning, and reshaping of the students’ scholarly selves. This identity work mirrors the complexities induced by the internationalization of doctoral pedagogies. We present the students’ identity work here to illuminate extant practice and further study of internationalized doctoral education

A method for Absolute Protein Expression Quantity Measurement Employing Insulator RiboJ

Measuring the absolute protein expression quantity for a specific promoter is necessary in the fields of both molecular biology and synthetic biology. The strength of a promoter is traditionally characterized by measuring the fluorescent intensity of the fluorescent protein downstream of the promoter. Until now, measurement of the absolute protein expression quantity for a promoter, however, has been unsuccessful in synthetic biology. The fact that the protein coding sequence influences the expression level for different proteins, and the inconvenience of measuring the absolute protein expression level, present a challenge to absolute quantitative measurement. Here, we introduce a new method that combines the insulator RiboJ with the standard fluorescence curve in order to measure the absolute protein expression quantity quickly; this method has been validated by modeling verification. Using this method, we successfully measured nine constitutive promoters in the Anderson promoter family. Our method provides data with higher accuracy for pathway design and is a straightforward way to standardize the strength of different promoters. Keywords: RiboJ, Promoter measurement, Synthetic biolog

H2 formation via non-Born-Oppenheimer hydrogen migration in photoionized ethane

Abstract Neutral H2 formation via intramolecular hydrogen migration in hydrocarbon molecules plays a vital role in many chemical and biological processes. Here, employing cold target recoil ion momentum spectroscopy (COLTRIMS) and pump-probe technique, we find that the non-adiabatic coupling between the ground and excited ionic states of ethane through conical intersection leads to a significantly high yield of neutral H2 fragment. Based on the analysis of fingerprints that are sensitive to orbital symmetry and electronic state energies in the photoelectron momentum distributions, we tag the initial electronic population of both the ground and excited ionic states and determine the branching ratios of H2 formation channel from those two states. Incorporating theoretical simulation, we established the timescale of the H2 formation to be ~1300 fs. We provide a comprehensive characterization of H2 formation in ionic states of ethane mediated by conical intersection and reveals the significance of non-adiabatic coupling dynamics in the intramolecular hydrogen migration