研究目的
Demonstrating the production of long-lived octafluoronaphthalene pentacation radical in gas phase by tunneling ionization using 1.4 μm femtosecond laser pulses and identifying multiply charged molecular cations definitively by their m/z, isotopic structure, and peak shape using time-of-flight mass spectrometry.
研究成果
The production of pentacation radical of octafluoronaphthalene in intense femtosecond laser fields was demonstrated based on the m/z, isotope peak, isotopic structure, and peak shape. The use of perfluoro-aromatics is a promising way to approach intact highly charge states. The lower limit of the lifetime of pentacation radical is estimated to be 11 μs.
研究不足
The error in the determination of absolute laser intensity was about ± 10%. The error in the evaluation of the ion yield was approx. ± 5%. The lifetime of pentacation radical was estimated to be at least 11 μs, but the exact lifetime is not known.
1：Experimental Design and Method Selection:
The multiple ionization of C10F8 and xenon was carried out with a 30-fs pulse centered at
2：8 μm and a 40-fs pulse centered at 4 μm. The laser beam was focused into the ionization chamber with a planoconvex quartz lens of 200 mm focusing length. The ions were detected by a linear mode of Wiley–Mclaren type time-of-flight mass spectrometer (TOF-MS) equipped with a MCP detector. Sample Selection and Data Sources:
Octafluoronaphthalene (C10F8, Aldrich, 96%) and xenon (Japan Air Gases,
3：99%) were used as received. List of Experimental Equipment and Materials:
Thales laser (Alpha 100/1000/XS hybrid), second-order single-shot autocorrelator (Thales laser, TAIGA), optical parametric amplifier (Quantronix, TOPAS), second-order scanning autocorrelator (APE, PulseCheck), linear mode of Wiley–Mclaren type time-of-flight mass spectrometer (TOF-MS, Toyama, KNTOF-1800), MCP detector (Hamamatsu Photonics, F4655-11X).
4：Experimental Procedures and Operational Workflow:
The laser beam was focused into the ionization chamber, and the ions were detected by TOF-MS. The actual laser intensity at the focus was determined by measuring the saturation intensity of xenon. The m/z scale was calibrated by using xenon ion peaks.
5：Data Analysis Methods:
The molecular ion yield was obtained by integrating over the appropriate peak in the TOF spectrum.
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