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

为了检验多脉冲序列和脉冲整形技术控制化学反应的潜力，采用最佳脉冲整形技术对苝晶体的激发过程和激发态进行了研究。我们成功地控制了α-苝晶体的发射光谱特征；在不改变y发射强度的情况下，e发射强度增加了1.4倍。此外，我们还发现了一种多光子激发效率比单飞秒脉冲高两倍的近红外脉冲形状。结果表明，脉冲序列和脉冲整形技术可以控制凝聚态分子的激发过程。为了通过增加脉冲能量来扩展脉冲整形技术的应用领域，尝试用BBO晶体对传统再生放大器获得的飞秒脉冲进行X^<(2)>:X^<(2)>工艺压缩。莫尔意识到，120秒的脉冲宽度被缩小到80秒左右。为了寻找可以应用脉冲整形技术的分子体系，对几种分子吸附表面体系进行了时间分辨实验。研究发现，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种短寿命物质。从OD波段强度的时间行为来看，异丁烯的解吸发生在OD模式的振动松弛结束后，系统达到热平衡之前。在c(4×2)-CO/Ni（111）体系中，CO分子在近红外强脉冲的照射下从空心位点跳到顶部位点。跳跃现象完全是短暂的，表面在几百皮秒内返回到预激发态而没有解吸。利用和频产生（SFG）光谱研究了在超高真空条件下，近红外泵浦脉冲作用下，10层D_2O冰在CO/Pt（111）上130 K的瞬态响应。结果表明，在不解吸的情况下，冰晶层中的D_2O分子在泵送过程中形成非晶状或液态结构，晶体在亚纳秒的时间尺度上恢复到晶体结构。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