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Ya Cheng - One of the best experts on this subject based on the ideXlab platform.

  • gain dynamics of a free space Nitrogen Laser pumped by circularly polarized femtosecond Laser pulses
    Optics Express, 2014
    Co-Authors: Jinping Yao, Hongqiang Xie, Bin Zeng, Wei Chu, Haisu Zhang, Chenrui Jing, Chaojin Zhang, Ya Cheng
    Abstract:

    We experimentally demonstrate ultrafast dynamic of generation of the 337-nm Nitrogen Laser by injecting an external seed pulse into a femtosecond Laser filament pumped by a circularly polarized Laser pulse. In the pump-probe scheme, it is revealed that the population inversion between the C3Πu and B3Πg states of N2 for the free-space 337-nm Laser is firstly built up on the timescale of several picoseconds, followed by a relatively slow decay on the timescale of tens of picoseconds, depending on the Nitrogen gas pressure. By measuring the intensities of 337-nm signal from Nitrogen gas mixed with different concentrations of oxygen gas, it is also found that oxygen molecules have a significant quenching effect on the Nitrogen Laser signal. Our experimental observations agree with the picture of electron-impact excitation.

  • gain dynamics of a free space Nitrogen Laser pumped by circularly polarized femtosecond Laser pulses
    arXiv: Optics, 2014
    Co-Authors: Jinping Yao, Hongqiang Xie, Bin Zeng, Wei Chu, Haisu Zhang, Chenrui Jing, Chaojin Zhang, Ya Cheng
    Abstract:

    We experimentally demonstrate ultrafast dynamic of generation of a strong 337-nm Nitrogen Laser by injecting an external seed pulse into a femtosecond Laser filament pumped by a circularly polarized Laser pulse. In the pump-probe scheme, it is revealed that the population inversion between the excited and ground states of N2 for the free-space 337-nm Laser is firstly built up on the timescale of several picoseconds, followed by a relatively slow decay on the timescale of tens of picoseconds, depending on the Nitrogen gas pressure. By measuring the intensities of 337-nm signal from Nitrogen gas mixed with different concentrations of oxygen gas, it is also found that oxygen molecules have a significant quenching effect on the Nitrogen Laser signal. Our experimental observations agree with the picture of electron-impact excitation.

  • real time observation of dynamics in rotational molecular wave packets by use of air Laser spectroscopy
    Physical Review A, 2014
    Co-Authors: Bin Zeng, Haisu Zhang, Chenrui Jing, Guihua Li, Jielei Ni, Ya Cheng
    Abstract:

    (Received 26 January 2014; published 21 April 2014)Molecular rotational spectroscopy based on a strong-field-ionization-induced Nitrogen Laser is employed toinvestigate the time evolution of the rotational wave packet composed by a coherent superposition of quantumrotationalstatescreatedinafield-freemolecularalignment.Weshowthatthistechniqueuniquelyallowsreal-timeobservation of the ultrafast dynamics of the molecular rotational wave packet. Our analysis also shows that thereexist two channels of generation of the Nitrogen Laser, shedding light on the population inversion mechanismbehind the air Laser generated by intense femtosecond Laser pulses.DOI: 10.1103/PhysRevA.89.042508 PACS number(s): 33

Jentaie Shiea - One of the best experts on this subject based on the ideXlab platform.

  • using electrospray assisted Laser desorption ionization mass spectrometry to characterize organic compounds separated on thin layer chromatography plates
    Analytical Chemistry, 2007
    Co-Authors: Shuyao Lin, Minzong Huang, Huichiu Chang, Jentaie Shiea
    Abstract:

    Electrospray-assisted Laser desorption/ionization (ELDI), an ionization method that combines Laser desorption and electrospray ionization (ESI), can be used under ambient conditions to characterize organic compounds (including FD&C dyes, amines, extracts of a drug tablet) separated in the central track on a thin-layer chromatography (TLC) plate coated with either reversed-phase C18 particles or normal-phase silica gel. After drying, the TLC plate was placed on an acrylic sample holder set in front of the sampling skimmer of an ion trap mass analyzer. The chemicals at the center of the TLC plate were analyzed by pushing the sample holder into the path of a Laser beam with a syringe pump. The molecules in the sample spot were desorbed by continuously irradiating the surface of the TLC plate with a pulsed Nitrogen Laser. Then, the desorbed sample molecules entered an ESI plume where they were ionized through the reactions with the charged species (including protons, hydronium ions and their cluster ions, sol...

  • electrospray assisted Laser desorption ionization mass spectrometry for direct ambient analysis of solids
    Rapid Communications in Mass Spectrometry, 2005
    Co-Authors: Jentaie Shiea, Minzon Huang, Chenghui Yuan, Iwona B Beech, Jan Sunner
    Abstract:

    A new method of electrospray-assisted Laser desorption/ionization (ELDI) mass spectrometry, which combines Laser desorption with post-ionization by electrospray, was applied to rapid analysis of solid materials under ambient conditions. Analytes were desorbed from solid metallic and insulating substrata using a pulsed Nitrogen Laser. Post-ionization produced high-quality mass spectra characteristic of electrospray, including protein multiple charging. For the first time, mass spectra of intact proteins were obtained using Laser desorption without adding a matrix. Bovine cytochrome c and an illicit drug containing methaqualone were chosen in this study to demonstrate the applicability of ELDI to the analysis of proteins and synthetic organic compounds.

Bin Zeng - One of the best experts on this subject based on the ideXlab platform.

  • gain dynamics of a free space Nitrogen Laser pumped by circularly polarized femtosecond Laser pulses
    Optics Express, 2014
    Co-Authors: Jinping Yao, Hongqiang Xie, Bin Zeng, Wei Chu, Haisu Zhang, Chenrui Jing, Chaojin Zhang, Ya Cheng
    Abstract:

    We experimentally demonstrate ultrafast dynamic of generation of the 337-nm Nitrogen Laser by injecting an external seed pulse into a femtosecond Laser filament pumped by a circularly polarized Laser pulse. In the pump-probe scheme, it is revealed that the population inversion between the C3Πu and B3Πg states of N2 for the free-space 337-nm Laser is firstly built up on the timescale of several picoseconds, followed by a relatively slow decay on the timescale of tens of picoseconds, depending on the Nitrogen gas pressure. By measuring the intensities of 337-nm signal from Nitrogen gas mixed with different concentrations of oxygen gas, it is also found that oxygen molecules have a significant quenching effect on the Nitrogen Laser signal. Our experimental observations agree with the picture of electron-impact excitation.

  • gain dynamics of a free space Nitrogen Laser pumped by circularly polarized femtosecond Laser pulses
    arXiv: Optics, 2014
    Co-Authors: Jinping Yao, Hongqiang Xie, Bin Zeng, Wei Chu, Haisu Zhang, Chenrui Jing, Chaojin Zhang, Ya Cheng
    Abstract:

    We experimentally demonstrate ultrafast dynamic of generation of a strong 337-nm Nitrogen Laser by injecting an external seed pulse into a femtosecond Laser filament pumped by a circularly polarized Laser pulse. In the pump-probe scheme, it is revealed that the population inversion between the excited and ground states of N2 for the free-space 337-nm Laser is firstly built up on the timescale of several picoseconds, followed by a relatively slow decay on the timescale of tens of picoseconds, depending on the Nitrogen gas pressure. By measuring the intensities of 337-nm signal from Nitrogen gas mixed with different concentrations of oxygen gas, it is also found that oxygen molecules have a significant quenching effect on the Nitrogen Laser signal. Our experimental observations agree with the picture of electron-impact excitation.

  • real time observation of dynamics in rotational molecular wave packets by use of air Laser spectroscopy
    Physical Review A, 2014
    Co-Authors: Bin Zeng, Haisu Zhang, Chenrui Jing, Guihua Li, Jielei Ni, Ya Cheng
    Abstract:

    (Received 26 January 2014; published 21 April 2014)Molecular rotational spectroscopy based on a strong-field-ionization-induced Nitrogen Laser is employed toinvestigate the time evolution of the rotational wave packet composed by a coherent superposition of quantumrotationalstatescreatedinafield-freemolecularalignment.Weshowthatthistechniqueuniquelyallowsreal-timeobservation of the ultrafast dynamics of the molecular rotational wave packet. Our analysis also shows that thereexist two channels of generation of the Nitrogen Laser, shedding light on the population inversion mechanismbehind the air Laser generated by intense femtosecond Laser pulses.DOI: 10.1103/PhysRevA.89.042508 PACS number(s): 33

Peter Roepstorff - One of the best experts on this subject based on the ideXlab platform.

N L Gilfrich - One of the best experts on this subject based on the ideXlab platform.

  • design and performance of a matrix assisted Laser desorption time of flight mass spectrometer utilizing a pulsed Nitrogen Laser
    Analytica Chimica Acta, 1991
    Co-Authors: R S Brown, N L Gilfrich
    Abstract:

    Abstract The design considerations and experimental performance of a linear time-of-flight mass spectrometer are reported for performing matrix-assisted Laser desorption studies. A simple pulsed gas-discharge Nitrogen Laser (337.1 nm) is successfully used in contrast to the more widely used frequency-quadrupled (266 nm) or frequency-tripped (355 nm) Nd : YAG solid-state Laser. Optical considerations in utilizing the pulsed Nitrogen Laser are discussed and a simple optical arrangement is described which allows for suitable imaging of the poor spartial beam profile of the pulsed Nitrogen Laser. Laser spot sizes of 150 × 450 μm are obtainable. As with the frequency-tripled Nd : YAG Laser, sinapinic acid is found to be the most useful matrix for producing protonated molecular species from proteins. Appropriate Laser power levels are determined, as are matrix/sample levels. Adequate response for most small to medium molecular weight proteins are obtained for less than 1 pmol of sample. A simple einsel lens incorporated into the ion source does not appear to provide any significant focusing of the Laser-desorbed ions; however, a constant d.c. voltage applied to beam steering plates enhances the ion signal significantly. Selective, pulsed deflection of the low-mass ions produced from the matrix is also utilized to prevent excessive saturation of the microchannel plate ion detector. High source potentials are found to provide improved resolution and sensitivity in comparison with lower source potentials combined with post-acceleration at the detector. Representative mass spectra of several proteins and peptides are presented. Increased formation of photoinduced adduct ions are observed in comparison with that reported for matrix-assisted Laser desorption experiments utilizing a Nd : YAG Laser and significant amounts of dimer and trimer ions are produced. The former may be due to non-optimized sample/matrix compositions as opposed to wavelength-induced effects, whereas the latter is only observed at higher protein concentrations. Significantly more peak broadening than would normally be expected is observed above 20 000 u. This may be due to the post-acceleration design of the microchannel plate detector used.