Application of Pulse-Shaping and Multi-Pulse-Train for Control of Chemical Reaction in Condensed Phase and Surface

为了考察多脉冲串和脉冲整形技术在化学反应控制中的潜力，利用优化的脉冲整形技术研究了激发过程和激发态的控制。我们成功地控制了α-P晶体的发射光谱特征，在不改变Y发射强度的情况下，电子发射强度提高了1.4倍。此外，我们还发现了一种近红外脉冲形状，它的多光子激发效率比单个飞秒脉冲的激发效率高出两倍。这些结果表明，脉冲串和脉冲整形技术可以控制凝聚相分子的激发过程。为了通过提高脉冲能量来扩大脉冲整形技术的应用范围，尝试用BBO晶体对从传统再生放大器获得的飞秒脉冲进行压缩。这是r…为了寻找可以应用脉冲整形技术的分子体系，在几个分子吸附表面体系上进行了时间分辨实验。在异丁烯吸附的沸石体系中，异丁烯吸附的OD基团通过振动激发产生了一个短寿命物种。从OD带强度的时间行为来看，异丁烯的脱附发生在OD模的振动弛豫结束后，体系达到热平衡之前。在c(4×2)-CO/Ni(111)体系中，CO分子在强近红外脉冲的照射下发生了由空位到顶位的跃迁。跳跃现象被发现是完全瞬时的，表面在几百皮秒内返回到预激发态而没有解吸。在超高真空条件下，用和频(SFG)谱研究了10个D2O冰分子层在130K下CO/Pt(111)表面的和频抽运响应。结果表明，冰晶层中的D2O分子在抽运过程中形成无定形或类液体结构，晶体在亚纳秒尺度上恢复到晶体结构。较少

In order to examine the potentiality of multi pulse train and pulse shaping technique for control of chemical reaction, control of excitation process and excited states of perylene crystal was investigated by optimal pulse shaping technique. We succeeded in controlling the emission spectral feature of an α-perylene crystal ; the intensity of E-emission was increased by a factor of 1.4 without the change of Y-emission intensity. Furthermore, we found a near-infrared pulse shape whose multi-photon excitation efficiency is larger than that of a single femtosecond pulse by a factor of two. It was concluded from these results that pulse train and pulse shaping technique can control excitation process of molecules in condensed phase. In order to extend the application area of the pulse-shaping technique by increasing the pulse energy, the compression of femtosecond pulses obtained from a conventional regenerative amplifier was attempted by X^<(2)>:X^<(2)> process using BBO crystals. It was r … More ealized that the pulse width of 120 fs was narrowed to about 80 fs.For the search of the molecular system which can be applied by the pulse shaping technique, the time-resolved experiments were carried out on several molecular-adsorbed-surface systems. It was found on isobutene adsorbed zeolite system that a short-lived species is produced by vibrational excitation of isobutene adsorbed OD groups. From the temporal behavior of OD band intensity, the desorption of isobutene takes places after the vibrational relaxation of OD mode finishes and before the system reaches thermal equilibrium. On the c(4×2)-CO/Ni(111) system, it was found that the site-hopping of CO molecule from hollow site to atop site was induced by the irradiation of intense near-infrared pulses. The hopping phenomenon was found to be entirely transient, with the surface returning to the pre-excited state within a few hundred picoseconds without desorption. The transient response of 10 molecular layers of D_2O ice on CO/Pt(111) at 130 K was also investigated under ultra-high vacuum following a near-infrared pump pulse by sum frequency generation (SFG) spectroscopy. It was revealed that the D_2O molecules in the ice crystalline layer formed an amorphous or liquid-like structure in response to the pumping without desorption of D_2O to the gas phase, and the crystals returned to the crystal structure on a sub-nanosecond time scale. Less