Minimum structure of high-order harmonic spectrum from molecular multi-orbital effects involving inner-shell orbitals.

The spectral features of high-order harmonic spectra can provide rich information for probing the structure and dynamics of molecules in intense laser fields. We theoretically study the high harmonic spectrum with the laser polarization direction perpendicular to the N2O molecule and find a minimum structure in the plateau region of the harmonic spectrum. Through analyzing the time-dependent survival probability of different electronic orbitals and the time-dependent wave packet evolution, it is found that this minimum position is caused by the harmonic interference of HOMO a, HOMO-1, and HOMO-3 a orbitals. Moreover, this interference minimum is discovered over a wide frequency range of 0.087 a.u. to 0.093 a.u., as well as a range of driving laser intensities with peak amplitudes between 0.056 a.u. and 0.059 a.u.. This study sheds light on the multi-electron effects and ultrafast dynamics of inner-shell electrons in intense laser pulses, which are crucial for understanding and controlling chemical reactions in molecules.

Circularly polarized attosecond light generation from OCS molecules irradiated by the combination of linear polarized infrared and orthogonal terahertz fields.

Researching ultrafast dynamics and creating coherent light sources will both benefit significantly from the establishment of polarization control in high-order harmonic generation (HHG). By employing the time-dependent density functional theory method, we investigate HHG of carbonyl sulfide molecules using a combination of a linear polarized infrared (IR) laser and a weaker orthogonal Terahertz (THz) field. Our findings show that by adjusting the amplitude of the THz field, the movement scale of electrons in the THz direction can be tuned, thereby one can control the harmonic intensity in the IR laser direction. This method allows for the creation of near-circularly polarized attosecond pulses. Furthermore, the ellipticity of the attosecond pulse may be changed by modifying the carrier-envelope phase of the IR laser pulse.

Calculation of high-order harmonic generation of atoms and molecules by combining time series prediction and neural networks.

High-order harmonic generation (HHG) from the interaction of ultra-intense laser pulses with atoms is an important tabletop short-wave coherent light source. Accurate quantum simulations of it present large computational difficulties due to multi-electron multidimensional effects. In this paper, the time-dependent response of hydrogen atoms is calculated using a time-series prediction scheme, the HHG spectrum is reconstructed very accurately. The accuracy of the forecasting is further improved by using a neural network scheme. This scheme is also applied to the simulation of the harmonic emission on multi-electron systems, and the applicability of the scheme is confirmed by the harmonic calculation of complex systems. This method is expected to simulate the nonlinear dynamic process of multi-electron atoms and molecules irradiated by intense laser pulses quickly and accurately.

Identifying the Multielectron Effect on Chemical Bond Rearrangement of CH3Cl Molecules in Strong Laser Fields.

Strong field double ionization that triggers the chemical bond rearrangement of CH3Cl is investigated by impulsive control of the alignment of molecules. The alignment and laser intensity dependent H2+ and H3+ yields in linearly polarized femtosecond laser have been measured, and the obtained data show that the maximum signal of H2+ appears at the laser polarization parallel to the C-Cl axis of molecules and H3+ species are more likely to eject at the laser polarization parallel to the C-Cl axis at low laser intensity while the H3+ signal peaks at laser polarization perpendicular to the C-Cl axis at high laser intensity. The measurements indicate that electrons from HOMO - 1 and HOMO - 2 orbitals have been ionized for the generation of bond rearrangement at different laser intensity. Our results demonstrate the importance of multielectron effects and also provide an effective control method in the process of chemical bond rearrangement of the molecules in strong laser fields.

Expression profiles of five FT-like genes and functional analysis of PhFT-1 in a Phalaenopsis hybrid

Background: Phalaenopsis is an important ornamental flowering plant that belongs to the Orchidaceae family and is cultivated worldwide. Phalaenopsis has a long juvenile phase; therefore, it is important to understand the genetic elements regulating the transition from vegetative phase to reproductive phase. In this study, FLOWERING LOCUS T (FT) homologs in Phalaenopsis were cloned, and their effects on flowering were analyzed. Results: A total of five FT-like genes were identified in Phalaenopsis. Phylogenetic and expression analyses of these five FT-like genes indicated that some of these genes might participate in the regulation of flowering. A novel FT-like gene, PhFT-1, distantly related to previously reported FT genes in Arabidopsis and other dicot crops, was also found to be a positive regulator of flowering as heterologous expression of PhFT-1 in Arabidopsis causes an early flowering phenotype. Conclusions: Five FT homologous genes from Phalaenopsis orchid were identified, and PhFT-1 positively regulates flowering.