碎片

Excitation functions of neutron, proton and α particle emission prior to scission measured in the reactions 28 Si+ 164,167,170 Er→ 192,195,198 Pb are studied using an extensive fission diffusion model and it is found that the model can well describe the trend of particle multiplicities of Pb isotopes measured experimentally as a function of the bombarding energy,which indicates the existence of isotope effects in prescission particle emission.

用推广的裂变扩散模型研究了2 8Si+16 4，16 7，170 Er→192 ，195，198Pb反应中测量的断前中子、质子和α粒子多重性的激发函数。发现扩散模型能很好地拟合这些轻粒子多重性随裂变系统激发能和Pb同位素的变化趋势。表明断前粒子发射存在一个同位素效应。进而在一个考虑了裂变过程中摩擦效应的统计模型的框架内，在In和Er这两个元素的同位素链中，考察了同位素效应与裂变碎片质量不对称性和裂变系统尺度的关系。计算结果表明：同位素效应的存在不依赖于裂变系统的大小和不对称性。此外，当裂变系统具有高的中质比时，轻带电粒子发射将不再敏感于裂变延迟时间的长短，而中子发射则非常敏感。

Therefore, there're only single charged parent ions of the sample gas molecule under the condition of photons' irradiation effect, and no fragment ions produced. Consequently, the mass spectra obtained from photoionization is very simple, and the sample gas can be detected without preseparation.

样品气体分子在光子的照射作用下只产生单电荷母离子，不产生碎片离子，以该电离方式获得的质谱图非常简单，因此气体样品不需分离即可进行检测。

The first step in the degradation is most probably the classical ester scission reaction to give a carboxylic acid and olefinic end groups. Further ester scission on the adjacent ester groups of carboxylic acid and olefinic molecular chains can then lead to the formation of lower weight pyrolytic products, such as: CH〓=CHOCOPhCOOCH=CH〓、CH〓=CHOCOPhCOOH and HOOCPhCOOH, and they can pyrolyze continually to produce substrate pyrolytic compounds, such as: HOOCPhCOCH〓、PhCOOH、PhH、PhCOCH〓 and CO、CO〓. At the same time, a corsslinking cyclization reaction occurred of the formation of the gas products during the degradation of PET.

断裂大分子链端邻近羰基和乙烯基的酯键持续断裂，不断地形成小分子裂解产物，如：CH〓=CHOCOPhCOOCH=CH〓、CH〓=CHOCOPhCOOH以及HOOCPhCOOH，这些产物还会进一步裂解成分子量更低的小分子裂解产物，如：HOOCPhCOCH〓、PhCOOH、PhH、PhCOCH〓以及CO、CO〓等，与此同时，一部分乙烯基酯端基的大分子链碎片会发生支化而相互连接，再经&链脱离&和环化反应形成难燃的交联产物。

It was but yesterday I thought myself a fragment quivering without rhythm in the sphere of life.

就在昨天，我以为自己是一只碎片，在生命的苍穹里，毫无节奏的颤动。

It was but yesterday I thought myself a fragment quivering without rhythm in the sphere of life.

仅仅是昨天，我以为自己是在生命的天空里毫无节奏地颤动的碎片。

I t was but yesterday I thought myself a fragment quivering without rhythm in the sphere of life.

仅仅在昨天，我认为我自己只是一个碎片，无韵律地在生命的穹苍中颤抖。

It was but yesterday I thought myself a fragment quivering without rhythm in the sphere of life.

仅仅在昨日，我还认为自己是一片碎片，在生命的天空中了无韵律地颤动。

It was but yesterday I thought myself a fragment quivering without rhythm in the sphere of life.

仅仅在昨日，我还以为自己是一片碎片，在生命的天空中无韵律地颤动。

It was yesterday I thought myself a fragment quivering without rhythm in the sphere of life.

仅仅在昨日，我还以为自己是一片碎片，在生命的天空中无旋律的颤动。

It was but yesterday I thought myself a fragment quivering without rhythm in the sphere of life.

还在昨天，我觉得自己只是一块碎片，在生命的苍穹中毫无节奏地颤动着。

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。