【作者】 张少华；

【导师】 陈旸；

【作者基本信息】 中国科学技术大学 ， 化学物理， 2009， 博士

【摘要】 本论文主要包括两部分内容:过渡金属硫化物的激光诱导荧光谱研究和液相大分子的时间分辨红外光谱及动力学研究。在过渡金属硫化物的激光诱导荧光谱研究部分我们采用脉冲直流放电和超声射流技术相结合的方法制备了CuS和FeS等3d过渡金属硫化物,采集并分析了它们在可见波段的激光诱导光谱（LIF）激发谱,分析结果如下:CuS自由基的激光诱导荧光激发谱利用Cu针电极脉冲直流放电产生Cu原子与CS₂/Ar样品气体在超声射流条件下反应产生CuS自由基,记录并研究了它在17200-9500 cm^-1能量范围内的激光诱导荧光激发谱,共观测到的14个谱带,其中11个为新发现的谱带。通过对谱带的振转分析,将这14个谱带标识为: （?）（v’’=0）,（?）（v’’=1）和（?）（v’’=0）三个不同的跃迁。根据光谱的转动结构拟合得到了较为精确的A²∑^-电子态的光谱常数并讨论了此电子激发态的可能电子组态及构型。此外,我们还测量得到了大部分谱带在无碰撞条件下的自然寿命。FeS自由基的激光诱导荧光激发谱采用脉冲直流放电和超声射流技术,利用Fe制针电极放电产生Fe原子与H₂S/Ar混合的样品气体反应产生FeS自由基,首次记录并研究了它在18 800-21 600 cm^-1能量范围内的激光诱导荧光激发谱,对观测到的50个谱带进行了振动归属,并对它们之中的48个谱带进行了转动分析,得到这些谱带转动常数,它们被归属为七个振动跃迁序列,其中包括从Fe⁵⁶S³²电子基态。⁴△跃迁四个不同上态的平行跃迁序列及其中一个来自于同位素分子Fe⁵⁴S³²的平行跃迁和两个Ω=5←Ω=4的垂直跃迁序列。用起始谱带带头未来标识分别为:[19.25]⁵△₄-X⁵△₄（v’=3-11-v"=0）,[19.42]⁵△₄-X⁵△₄（v’=-0-7-v’’=0）,[18.99]⁵△₄-X⁵△₄（v’=0-8缺7-v’’=0）,[19.61]⁵△₄-X⁵△₄（v’=0-6-v"=0）,[20.15]⁵△₄-X⁵△₄(Fe⁵⁴S³²)（v’=6-10-v’’=0）以及[19.32]⁵Φ₄-X⁵△₄（v’=0-7-v"=0）和[19.73]⁵Φ₅-X⁵△₄（v’=0-4-v’’=0）。根据光谱的转动结构拟合得到了所有上电子态的光谱常数并讨论了它们的可能电子组态及构型。此外,通过对荧光寿命的测量我们还得到了大部分谱带在无碰撞条件下的自然寿命。在液相大分子的时间分辨红外光谱及动力学研究部分里,我们先是采用激光诱导温度跃变结合时间分辨的中红外激光光谱的研究手段首次采集到了1600-1700cm^-1波段内PNIPAM的瞬态红外吸收差谱,结合动力学的实验结果,重新归属了此波段内PNIPAM的吸收谱峰。并在此基础上进一步研究了10ns-1ms时间尺度内各特征吸收谱峰的动力学行为,以及不同浓度,不同链长对它们某些动力学行为特征时间的影响。首次同时观测到了长链PNIPAM分子随温度变化发生的coil-to-globule（包括快慢两个过程Ⅰ,Ⅱ）及相应可能为globule-to-coil的逆过程,并给出了它们各自的特征时间范围,并详细分析了其中coil-to-globule内过程Ⅰ,Ⅱ在不同条件下的特征时间。随后我们介绍了步进扫描的时间分辨傅立叶变换光谱仪（Step-Scantime-resolved FTIR,IFS/66S）的工作原理,以及为利用IFS66/S型FTIR光谱仪进行液相大分子相转变反应动力学的研究,我们尝试建设的一套脉冲激光诱导温度跃变与时间分辨的FTIR光谱相结合的实验装置。在此实验装置上我们已实现了D₂O液体的瞬态温度升高过程,并将其用于合成高分子PNIPAM在重水溶液中的相转变过程的研究,已观测到其酰胺峰Ⅰ’的吸收度随温度升高而发生的变化过程,与稳态及瞬态中红外激光吸收差谱中较为一致。证明了我们IFS66/S型FTIR光谱仪用于液相分子体系研究的可行性。更多还原

【Abstract】 This dissertation includes two parts: one is the experimental studies on the laser-induced fluorescence （LIF） excitation spectra of the 3d transition-metal sulfides; the other is the transient infrared spectroscopy on the macromolecular solutions by laser induced temperature jump technique.In the part of LIF excitation spectra, the CuS, and FeS molecules were produced by reaction of sputtered metal atoms with small molecule gas under supersonic jet cooled condition. The laser-induced fluorescence excitation spectra in visible region of them were recorded and analyzed. The main results are summarized as follows:The CuS molecules were produced by the reaction of CS₂ molecules with the copper atoms sputtered from a pair of pure copper pin electrodes under a pulsed DC discharge condition. The jet-cooled laser-induced fluorescence excitation spectra of CuS in the energy range of 17 200 - 19 500 cm^-1 were recorded and investigated. Fourteen vibronic bands were observed and rotationally analyzed, of which eleven bands were reported for the first time. Vibrational and rotational analyses indicated that the fourteen bands can be assigned to the A²∑^- （ v’ = 0 - 4 ） - X²∏_3/2 （v" =0, 1） and the A²∑^- （ v’ = 0 - 3 ） - X²∏_1/2 （ v" = 0 ） transitions. The molecular constants of these two electronic states were derived, and the isotopic shifts as well as the spin-splitting of the upper state were determined. In addition, the lifetimes of most newly observed bands were measured under the collision-free condition.The FeS molecules were produced by the reaction of H₂S molecules with the cobalt atoms sputtered from a pair of pure cobalt pin electrodes under a pulsed DC discharge condition. The jet-cooled laser-induced fluorescence excitation spectra of FeS in the energy range of 18 800 - 21 600 cm^-1 was recorded and studied for the first time. All of 50 vibronic bands were recorded, of which 48 vibronic bands were rotationally analyzed. Vibrational and rotational analyses indicated that the 46 bands can be assigned to the [19.25] ⁵△₄ （ v’ = 3 -11 ） - X⁵△₄（v" = 0）, [19.42]⁵△₄（ v’ = 0 - 7 ） - X⁵△₄ （v" = 0）, [18.99]⁵△₄ （V = 0 - 8, v’ =7 overlapped） - X⁵△₄ （v" = 0）, [19.61] ⁵△₄（v’ = 0 - 6 ） - X⁵△₄（v" = 0） and [19.32]⁵Φ₅ （ v’ = 0 - 7 ） - X⁵△₄ （v" = 0） ,[19.73] ⁵Φ₅ - X⁵△₄ （v’=0-4-v"=0）transitions. In addition, a few weaker bands also indicated as arising fromFe⁵⁴S³² [20.15]⁵△₄ （v’ = 6-10）-X ⁵△₄ （v" = 0）. The molecular constants of these all upper electronic excited states were derived. The possible electronic configurations of all upper states have been discussed. Furthermore, the lifetimes of most observed bands were measured under the collision-free condition.In the part of the transient infrared spectroscopy, combining the laser induced temperature jump and the time-resolved MIR laser spectroscopy, the transient time-resolved IR difference spectroscopy of N-isopropylacrylamide （PNIPAM） solution was recorded and analyzed for the first time. The bands in 1570-1700cm^-1 were reassigned. The fast transitional kinetics of typical peaks was investigated and an apparent multistep in the coil-to-globule transitional process was observed. From our data, the transitional process of PNIPAM contains three steps at least in millisecond timescale. According to theoretical models, the three steps were corresponded to the quick formation of small locally collapsed nuclei on the chain; the growth of these nuclei into clusters and the anti-process: the globule-to-coil process respectively. These conclusions were confirmed and explored by further studies which related with the different concentration and different chain length samples.Furthermore, for studying the coil-to-globule transitional process of macromolecular solutions with the Step-Scan time-resolved FTIR spectrometer （IFS66/S）, we designed and set up an experimental apparatus combining the laser induced temperature jump with the time-resolved FTIR spectrometer. On this apparatus, we have observed the temperature jump process of the D₂O and the coil-to-globule transitional process of the PNIPAM solution. All results are mainly consistent with the past known.更多还原