| 摘要: | 研究期間：10108~10207;As to my knowledge, the absolute frequencies of non-cascade two photon transition determined by direct femtosecond pulse-atom interaction, with ultra-high resolution (<50 kHz), was carried out by only two groups of which they were all the best groups in high-precision measurement, that is, the 2005 Nobel laureate in physics: T. Hansch and J. Hall (now is J. Ye's group). However, it puzzled scientists that, due to the high peak power of comb pulse, the AC stark shift might lead to wrong absolutely frequency measurement while this concern was not needed in their experiments. We are the most appropriate group to clarify this puzzle, since we have the best knowledge on cesium atom two photon spectra by CW laser, we are familiar with comb laser and we had experience on pulse shaping by using spatial light modulator, according to what we have published in the past five years. Therefore, the result of this project will be a very important reference in the metrological applications. Moreover, once the absolute frequency of cesium two photon transitions were precisely determined, it will bring a great impact in the metrological applications in terms of stabilizing the repetition rate of Ti:sapphire comb lasers against the cesium atom 6S-8S hyperfine transition. That means, a hand-sized low-cost diode laser system together with a cesium cell (~ NT 0.01 million total) could replace the Aglient synthesizer together with GPS based time-base acquisition system (~ 1.9 million toatl), even the stability of cesium clock standard (~ 8 million ). Also, once the aforementioned frequencies were determined, our Ti:sapphire laser system could be designed to be portable , which is already realized now for the most part, and to be sent to Dr. Yen-Chu Hsu's group in IAMS, Academia. We plan to real-time monitor the formation process of YC2 cluster by quickly resolving the molecular finger printing. To sum up, there are three key targets in this project: 1. Fundamental physics: clarify what is the role that ultrashort pulse played in terms of AC Stark shift, by comparing with the result from CW laser. 2.metrologications: to improve the accuracy and stability of comb laser repetition rate, which will bring near two order of magnitude cost down and convenient. 3. Demonstrate a wide-band high resolution finger printing in science by monitoring YC2 molecule gathering to cluster |
