The method of time-dependent quantum wave packet dynamics is used to calculate the femtosecond pump-probe photoelectron spectra and study the wave packet dynamic processes of the double-minimum potential state 6^1∑^...The method of time-dependent quantum wave packet dynamics is used to calculate the femtosecond pump-probe photoelectron spectra and study the wave packet dynamic processes of the double-minimum potential state 6^1∑^＋ of NaK in intense laser fields. The evolutions of the wave packet and the photoelectron energy spectra with time and internuclear distance are described in detail. The wave packet dynamic information of the 6^1∑^＋ state can be extracted from the photoelectron energy spectra.展开更多
Using a neutral N2 beam as target, this paper studies the dissociation of N2^＋ in intense femtosecond laser fields （45 fs, ～ 1 × 10^16 W/cm^2） at the laser wavelength of 800 nm based on the time-of-flight mas...Using a neutral N2 beam as target, this paper studies the dissociation of N2^＋ in intense femtosecond laser fields （45 fs, ～ 1 × 10^16 W/cm^2） at the laser wavelength of 800 nm based on the time-of-flight mass spectra of N＋ fragment ions. The angular distributions of N^＋ and the laser power dependence of N^＋ yielded from different dissociation pathways show that the dissociation mechanisms mainly proceed through the couplings between the metastable states （A, B and C） and the upper excited states of N^＋.A coupling model of light-dressed potential energy curves of N2^＋ is used to interpret the kinetic energy release of N^＋.展开更多
A train of three equally spaced femtosecond laser pulses is employed to control the photoionization/photodissociation processes of cyclopentanone. With the increase of pulse separation, a strong modulation of product ...A train of three equally spaced femtosecond laser pulses is employed to control the photoionization/photodissociation processes of cyclopentanone. With the increase of pulse separation, a strong modulation of product ion yield is observed. More than ten-fold changes of ion yield ratio between different products can be realized. The experimental observations further explain the compositions and formation pathways of peaks in the mass spectra. The controlling mechanisms are also discussed.展开更多
Heterovalent-metal doping is an efficient tool to tune the optoelectronic properties of the famous halide perovskites.Previous studies have focused on the heterovalent-doping in three-dimensional(3D) halide perovskite...Heterovalent-metal doping is an efficient tool to tune the optoelectronic properties of the famous halide perovskites.Previous studies have focused on the heterovalent-doping in three-dimensional(3D) halide perovskites.However, there is a lack of such doping in two-dimensional perovskites which possess unique optoelectronic properties and improved chemical stability as compared to 3D analogues.Here, we present successful doping of Bismuth into the lattice of lead-free, two-dimensional perovskite PEA2SnBr4 single crystals.Structural characterizations demonstrate that the doped crystals possess identical crystal structure and layered morphology with the pristine one.Intriguingly, we find the PL peak and spectral shape can be tailored by tuning the concentration of Bi dopants.Femtosecond transient absorption spectroscopy is performed to understand the underlying mechanism related to tunable PL behaviors, and a clear picture of the Bismuth-doping impact is provided.展开更多
Methanol was irradiated by 80 fs laser pulse, intensity range of 1013-1014 W/cm2. A TOF-mass spectrometer was coupled to the laser system and used to detect the ions produced. The parent ions CH3OH+ appeared firstly a...Methanol was irradiated by 80 fs laser pulse, intensity range of 1013-1014 W/cm2. A TOF-mass spectrometer was coupled to the laser system and used to detect the ions produced. The parent ions CH3OH+ appeared firstly at the laser intensity of 1.4 ×1013 W/cm2. While the laser intensity was gradually increased, the parent ions were dissociated and the primary ions CH2OH+ were given as verified from the irradiation of deuterated methanol (CH3OD) showing the C-H bond cracking firstly. While the laser intensity was further increased to 2.0 ×1013 W/cm2, the C-O bonds of the parent ions also broke to give CH3+. When the laser intensity was higher, smaller fragment ions like CH+, C+, OH+ and O+ also appeared. Among the fragment ions, only H+ ion yield had anisotropic angular distribution dependence on the laser polarization vector in the dissociation of methanol. All the experimental observations show that the dissociation of methanol proceeds through stepwise mechanism but not Coulomb explosion.展开更多
基金Project supported by the National Natural Science Foundation of China （Grant No 10374012）,
文摘The method of time-dependent quantum wave packet dynamics is used to calculate the femtosecond pump-probe photoelectron spectra and study the wave packet dynamic processes of the double-minimum potential state 6^1∑^＋ of NaK in intense laser fields. The evolutions of the wave packet and the photoelectron energy spectra with time and internuclear distance are described in detail. The wave packet dynamic information of the 6^1∑^＋ state can be extracted from the photoelectron energy spectra.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10774033,60878018 and 10674036)program for New Century Excellent Talents in University of China (NCET)
文摘Using a neutral N2 beam as target, this paper studies the dissociation of N2^＋ in intense femtosecond laser fields （45 fs, ～ 1 × 10^16 W/cm^2） at the laser wavelength of 800 nm based on the time-of-flight mass spectra of N＋ fragment ions. The angular distributions of N^＋ and the laser power dependence of N^＋ yielded from different dissociation pathways show that the dissociation mechanisms mainly proceed through the couplings between the metastable states （A, B and C） and the upper excited states of N^＋.A coupling model of light-dressed potential energy curves of N2^＋ is used to interpret the kinetic energy release of N^＋.
基金Project supported by the National Basic Research Program of China (973 Program) (Grant No.2013CB922200)the National Natural Science Foundation of China,(Grant Nos.10774056 and 10974070)+1 种基金the Fundamental Research Funds for the Central Universities,China (Grant No.200903371)the Specialized Research Fund for the Doctoral Program of Higher Education,China (Grant No.20100061110045)
文摘A train of three equally spaced femtosecond laser pulses is employed to control the photoionization/photodissociation processes of cyclopentanone. With the increase of pulse separation, a strong modulation of product ion yield is observed. More than ten-fold changes of ion yield ratio between different products can be realized. The experimental observations further explain the compositions and formation pathways of peaks in the mass spectra. The controlling mechanisms are also discussed.
基金supported by the National Key Research and Development Program of China (Grant No: 2016YFE0120900 and 2017YFA0204800)the National Natural Science Foundation of China (No.21,703,244, 21,403,226, and 21,533,010)+4 种基金DICP DMTO201601DICP ZZBS201703the Science Challenging Program (JCKY2016212A501)DICP Outstanding Postdoctoral Foundation (2016YB09)the China Postdoctoral Science Foundation (2017M611276)
文摘Heterovalent-metal doping is an efficient tool to tune the optoelectronic properties of the famous halide perovskites.Previous studies have focused on the heterovalent-doping in three-dimensional(3D) halide perovskites.However, there is a lack of such doping in two-dimensional perovskites which possess unique optoelectronic properties and improved chemical stability as compared to 3D analogues.Here, we present successful doping of Bismuth into the lattice of lead-free, two-dimensional perovskite PEA2SnBr4 single crystals.Structural characterizations demonstrate that the doped crystals possess identical crystal structure and layered morphology with the pristine one.Intriguingly, we find the PL peak and spectral shape can be tailored by tuning the concentration of Bi dopants.Femtosecond transient absorption spectroscopy is performed to understand the underlying mechanism related to tunable PL behaviors, and a clear picture of the Bismuth-doping impact is provided.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 29973052) the Ministry of Science & Technology of China.
文摘Methanol was irradiated by 80 fs laser pulse, intensity range of 1013-1014 W/cm2. A TOF-mass spectrometer was coupled to the laser system and used to detect the ions produced. The parent ions CH3OH+ appeared firstly at the laser intensity of 1.4 ×1013 W/cm2. While the laser intensity was gradually increased, the parent ions were dissociated and the primary ions CH2OH+ were given as verified from the irradiation of deuterated methanol (CH3OD) showing the C-H bond cracking firstly. While the laser intensity was further increased to 2.0 ×1013 W/cm2, the C-O bonds of the parent ions also broke to give CH3+. When the laser intensity was higher, smaller fragment ions like CH+, C+, OH+ and O+ also appeared. Among the fragment ions, only H+ ion yield had anisotropic angular distribution dependence on the laser polarization vector in the dissociation of methanol. All the experimental observations show that the dissociation of methanol proceeds through stepwise mechanism but not Coulomb explosion.
