Mizutani M, Tokeshi M, Hiraya A, Mitsuke K
lnstitute for Molecular Science, Myodaiji, Okazaki 444, Japan.
J Synchrotron Radiat. 1997 Jan 1;4(Pt 1):6-13. doi: 10.1107/S0909049596013520.
A mode-locked Ti:sapphire laser is made to oscillate at the frequency of the UVSOR storage ring, 90.115 MHz, in a multi-bunch operation mode. The third harmonic of the laser is available in the wavelength range 243-280 nm. Synchrotron radiation from an undulator is monochromated by a grazing-incidence monochromator and introduced coaxially with the laser. The temporal profile of the photon pulses is monitored in situ by a luminescing substance/photomultiplier combination. The delay timing between the laser and synchrotron radiation can be changed from 0 to 11 ns by adjusting an electronic module that provides phase-locked loop stabilization of the laser pulse. The reliability and feasibility of this laser-synchrotron radiation combination technique are demonstrated by applying pump-probe experiments to two physical systems. The first system is photodissociation of iodomethane (CHA) with a laser photon, followed by photoionization of I and CH3 fragments with synchrotron radiation. The second, two-photon ionization of He atoms, is studied as the prototype of a time-resolved experiment. The He+ signal counts as a function of the laser-synchrotron radiation delay are found to be enhanced in a narrow time window, which can be interpreted in terms of a short lifetime of the resonant state, He*(1s2p 1P), produced by primary synchrotron radiation excitation.
锁模钛宝石激光器在多束运行模式下，以90.115 MHz的频率振荡，该频率与UVSOR储存环的频率相同。激光的三次谐波在243 - 280 nm波长范围内可用。来自波荡器的同步辐射由掠入射单色仪单色化，并与激光同轴引入。光子脉冲的时间轮廓通过发光物质/光电倍增管组合进行原位监测。通过调整提供激光脉冲锁相环稳定的电子模块，激光与同步辐射之间的延迟时间可以在0到11 ns之间变化。通过将泵浦 - 探测实验应用于两个物理系统，证明了这种激光 - 同步辐射组合技术的可靠性和可行性。第一个系统是用激光光子使碘甲烷（CH₃I）光解离，然后用同步辐射使I和CH₃碎片光离子化。第二个系统是对氦原子的双光子电离，作为时间分辨实验的原型进行研究。发现作为激光 - 同步辐射延迟函数的He⁺信号计数在一个狭窄的时间窗口内增强，这可以根据由初级同步辐射激发产生的共振态He*(1s2p¹P)的短寿命来解释。
