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355nm Nd∶YAG激光在H_2中的高效一级斯托克斯转换 总被引:1,自引:1,他引:0
对脉冲Nd∶YAG激光(355 nm)在H2和H2∶He-Ar混合气体中的受激拉曼散射(SRS)进行了研究。在0.5 MPa的氢气中,同时测量到从二级反斯托克斯到三级斯托克斯的多波长输出,其总转化效率达88%;而高压下只剩下一级和二级斯托克斯输出,其中二级斯托克斯最大能量转化效率达44%(对应量子效率为63%)。由于高级斯托克斯的竞争,纯氢气中一级斯托克斯的最大能量转换效率不超过43%。通过向3 MPa氢气中掺入2 MPaAr气后,很好地抑制了二级斯托克斯的产生,从而获得了能量转换效率高达71%(对应量子效率为83%)的一级斯托克斯输出。对四波混频和级联受激拉曼散射在氢气多级斯托克斯产生中的作用以及惰性气体对它们的影响进行了讨论。 相似文献
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NH_3Ã(~1A_2~″)是一个快速预解离态, 以往的光谱研究从未得到它的转动分辨光谱。我们用两个脉冲染料激光器研究了NH_3C′→X的3+1多光子电离光谱和NH_3X→C′→Ã的折叠光学双共振多光子电离光谱, 称为“离子凹陷光谱”。对前者观察到了较高分辨的转动光谱, 得出C′v_2~′=O的高精度转动常数。通过谱线宽度, 得到了C′v_2~′=0,1,2能级的预解离寿命。从离子凹陷光谱上, 首次观察到了C′→Ã跃迁的0-0, 1-1, 2-2等带的转动分辨光谱。由双共振选择定则简化的光谱使漫散至~50 cm~(-1)线宽的转动线得以分开, 由此得到Ãv_2~″=0,1,2能级的转动常数和各谱带的带原点。在消除功率加宽的情况下, 测出Ãv_2~′=1能级的寿命。这种方法对研究分子的快速预解离态有一定的普遍意义。 相似文献
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The conversion efficiency of stimulated Raman scattering (SRS) in CH4 is studied by using a single longitudinal mode second-harmonic Nd:YAG laser (532 nm, linewidth 0.003 cm-1, pulse-width (FWHM) 6.5 ns).Due to the heat release from vibrationally excited particles, SRS processes often suffer from the thermal defocusing effect (TDE). In view of 6.5 ns laser pulse width is much shorter than the vibrational relaxation time of CH4 molecules, TDE can only affect the SRS processes afterwards. In the cases of low laser repetition, TDE will be not serious, because it will be removed by the thermal diffusion in Raman medium before the next pulse arrives. At the laser repetition rate 2 Hz, CH4 pressure 1.1 MPa and pump laser energy 95 m J, the quantum conversion efficiency of backward first-Stokes (BS1) has attained 73%. This represents the highest first-stokes conversion efficiency in CH4. Furthermore, due to the relaxation oscillation, the BS1pulses are narrowed to about 1.2 ns. As a result, the BS1 peak power turns out to be 2.7 times that of the pump. Its beam quality is also much better and is only slightly affected by TDE. This reason is that BS1 represents a wave-front-reversed replica of the pump beam, which can compensate the thermal distortions in Raman amplify process. Under the same conditions, but pump laser repetition rate as 10 Hz, the conversion efficiency of BS1 goes down to 36% due to TDE. From this study, we expect that a well-behaved 630 nm Raman laser may be designed by using a closed CH4/He circulating-cooling system, which may have some important applications. 相似文献
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用两束脉冲染料激光进行了CO的光学双共振四光子电离, 获得了转动分辩的CO A~(1Π)←X~(1Σ~+)和B~(1Σ~+)←A~(1Π)跃迁的光谱。观察到了在此2+1光子相继吸收中特有的选择定则。动力学研究表明CO基态到A~(1Π)态的双光子吸收是速率决定步骤, 其吸收截面约为1×10~(-49) cm~4 s。还测定了A~(1Π)态的单态转动传能截面。对于宇称指数e守恒、△J×±1的过程的截面约为0.05 nm; 随△J值增大而减小。对相同的△J, e正负变号的过程的截面总是小于e不变过程的截面。 相似文献
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研究了脉冲Nd:YAG激光(355 nm)泵浦的甲烷中多级Stokes光的产生和惰性气体对其转换效率的影响,其中一级和二级Stokes光的最大能量转换效率分别可达71%和38%(对应量子效率为79%和48%),大大高于已往文献报道的20%。在0.5 MPa下,可同时获得322 nm(3.6%),355 nm(24.5%),396 nm(24.3%),448 nm(22.3%)和515 nm(9.3%)的多波长输出。甲烷压力对多级Stokes转换有显著影响:高气压利于产生高效的一级Stokes光,而低气压则适合于高级Stokes光的产生。根据级联受激拉曼散射(SRS)和四波混频(FWM)理论对实验结果进行了分析,结果表明甲烷中高级Stokes光的产生是SRS和FWM协同作用的结果。加入的氦气增强了甲烷中Stokes光的转换效率,而氩气的作用恰恰相反,利用热透镜效应可以很好地解释这些现象。 相似文献