Selective excitation of the molecular rotational wave packet by two time-delayed laser pulses

In this paper, we investigate the control of the molecular wave packet of a linear molecule by two femtosecond laser pulses. It is shown that the odd and the even rotational wave packets created by a single laser pulse can be selectively excited by accurately controlling the time delay of another laser pulse. By inserting the peak of the second laser pulse at the position of maximum or minimum value around quarter or three quarter rotational period of the slope curve with odd （or even） rotational wave packet contribution that is created by the first laser pulse, the odd rotational wave packet can be enhanced （or suppressed） while the even rotational wave packet is suppressed （or enhanced）. As a result, the molecular alignments around quarter and three quarter rotational periods can be obtained. Moreover, it is also shown that by inserting the second laser pulse around the quarter or three quarter rotational periods, the changes in the maximum degree of the molecular alignment for the odd and the even rotational wave packet contributions are consistent with their corresponding slope curves at these positions.

An Automated,Highly Selective Reaction Monitoring Instrument Using Molecular Rotational Resonance Spectroscopy

Online monitoring of chemical reactions by using analytical chemistry tools is a powerful way to maximize control over these processes.In this paper,we demonstrate the use of molecular rotational resonance,an emerging and extraordinarily selective spectroscopic technique,to perform automated reaction monitoring measurements.An interface using a six-port valve with a calibrated sample loop,coupled to a temperature controlled inlet for analyte volatilization,was developed and tested.Two reactions were chosen for initial characterization:an amine-aldehyde condensation reaction to form an imine product and an isotopic exchange reaction of aβ-ketoester with keto-enol tautomerization.The spectrometer was able to provide kinetic information about the reaction and determine reaction completion.In the future,this system can be extended to detect and quantify impurities and characterize reaction selectivity,in addition to the reaction progress.

Thermal Energy-Driven Solid-State Molecular Rotation Monitored by Real-Time Emissive Color Switching

Inspired by nature’s molecular machines,the scientific research on solid-state molecular rotors is of great interest yet remains largely unexplored.Herein,we report a unique example of a thermal energydriven stimuli-responsive solid-state molecular rotor,which features an o-carborane moiety as a rotor that directly transduces the surrounding thermal energy into molecular rotations in the crystalline state.Its rotation is confirmed by X-ray diffraction.

NIR-absorbing superoxide radical and hyperthermia photogenerator via twisted donor-acceptor-donor molecular rotation for hypoxic tumor eradication

Hypoxia severely impedes the therapeutic efficacies of tumor chemotherapy, radiotherapy and conventional photodynamic therapy(type Ⅱ PDT). Herein, we proposed a nonplanar near-infrared(NIR)-absorbing hyperthermia and superoxide radical(O^(-)_(2)) photogenerator(TB) against hypoxic tumors. TB particularly possessed a favorable O^(-)_(2) generation capability under 808 nm laser irradiation with the donoracceptor-donor(D-A-D) molecular structure. Moreover, owing to molecular rotation, potent hyperthermia was realized under continuous laser irradiation. For the usage of hypoxic tumor treatment, TB was encapsulated by a block copolymer,poly(ethylene glycol)-b-poly(latic acid)(PEG_(45)-b-PLA_(24)), to fabricate phototheranostic nanoparticles(TB NPs). Due to the twisted molecular structure and the shielding effect of long alkyl chains, the π-π stacking-induced quenching of O^(-)_(2) could be reduced after the fabrication of nano-assemblies. Significantly, TB NPs exhibited satisfactory O^(-)_(2) generation for type I PDT and a simultaneously distinct photothermal conversion efficiency(PCE, 62%) for photothermal therapy(PTT)to combat hypoxic tumor cells. Moreover, the high PCE endowed TB NPs with high-performance photoacoustic(PA)and photothermal imaging capability. In vivo experiments demonstrated that TB NPs possessed an outstanding phototherapeutic efficacy for eradicating hypoxic tumors. This study established a novel approach for constructing oxygenindependent phototherapeutic reagent against hypoxic tumors.

State reconstruction of molecular spatial rotation

We establish a reconstruction approach for the rotational quantum state of linear molecules possessing a magnetic manifold. Our approximate method contains an iteration with generalized matrix inverses, processing the tomographic integral of the time-dependent molecular-axis distribution in a polar angle. As shown in a simulated example for an alignment state, the density matrix is determined in a high fidelity. An analytic tomographic formula is also derived for the symmetric top rotation. The state coherent in the quantum space of both the angular momentum and its magnetic projection can be approximately retrieved from the observable time-resolved solid-angle distribution of the molecular axis.

Optimal approach to rotational state reconstruction of linear molecules

We present a simulation for the reconstruction of the rotational quantum state of linear molecules to retrieve the density matrix. An optimal approach in the sense of minimal error limit is proposed, in which a variable set of angular frequency is properly chosen and the least square inversion is then applied. This approach of reconstruction from time-dependent molecular-axis angular distribution is proved adaptable for various object states, which has a good numerical stability independent of the selected rotational space.

The rotation and the phase transition in solid C60

The interaction between C-60's in solid C-60 has been calculated by (exp-6-1) potential, and the cause and the controlled factor of the high rapid rotations of C-60's were discussed. In order to describe the disordered degree of C-60 rotation, an equivalent M is introduced. The phase transitions at the similar to 260 K and at the similar to 90 K are studied from the viewpoint of C-60 rotation. The potential barriers of the ordered rotation below the similar to 260 K and the disordered rotation above the similar to 260 K have been given, and the effect of the external pressure on the temperature of phase transition has also been given.

Spatiotemporal rotational dynamics of laser-driven molecules

Molecular alignment and orientation by laser fields has attracted significant attention in recent years,mostly due to new capabilities to manipulate the molecular spatial arrangement.Molecules can now be efficiently prepared for ionization,structural imaging,orbital tomography,and more,enabling,for example,shooting of dynamic molecular movies.Furthermore,molecular alignment and orientation processes give rise to fundamental quantum and classical phenomena like quantum revivals,Anderson localization,and rotational echoes,just to mention a few.We review recent progress on the visualization,coherent control,and applications of the rich dynamics of molecular rotational wave packets driven by laser pulses of various intensities,durations,and polarizations.In particular,we focus on the molecular unidirectional rotation and its visualization,the orientation of chiral molecules,and the three-dimensional orientation of asymmetric-top molecules.Rotational echoes are discussed as an example of nontrivial dynamics and detection of prepared molecular states.

Synthesis,characterization,and phase transition of an inorganic-organic hybrid compound,[(3-nitroanilinium^＋)(18-crown-6)][IO4^-](CH3OH)

A novel inorganic-organic hybrid supramolecular compound,[（3-nitroanilinium^＋）（18-crown-6）][IO4]（CH3OH）（1）,was discovered as phase-transition materials displaying dielectric anomalous behaviors.The yellow block crystal formed by N-H…O hydrogen bonding that made contact through the cavity of 18-crown-6 was characterized by single-crystal X-ray diffraction,elemental analysis,infrared analysis,thermogravimetric analysis,differential scanning calorimetry,and potential-energy calculations.Differential scanning calorimetry measurements indicate that the compound experiences a reversible phase transition at around 220 K.Temperature-dependent dielectric measurements further confirm the phase transitions.Potential-energy calculations demonstrate that the phase transition occurs due to the molecular order-disorder rotation of CH3OH,whereas the space grouping of the crystal remains unchanged.

Structural relaxation and glass transition behavior of binary hard-ellipse mixtures

Structural relaxation and glass transition in binary hard-spherical particle mixtures have been reported to exhibit unusual features depending on the size disparity and composition. However, the mechanism by which the mixing effects lead to these features and whether these features are universal for particles with anisotropic geometries remains unclear. Here, we employ event-driven molecular dynamics simulation to investigate the dynamical and structural properties of binary two-dimensional hard-ellipse mixtures. We find that the relaxation dynamics for translational degrees of freedom exhibit equivalent trends as those observed in binary hard-spherical mixtures. However, the glass transition densities for translational and rotational degrees of freedom present different dependencies on size disparity and composition. Furthermore,we propose a mechanism based on structural properties that explain the observed mixing effects and decoupling behavior between translational and rotational motions in binary hard-ellipse systems.