The Turn Over of the Odd-even Pattern in Mass Spectra of Carbon Cluster Anions

摘要：

Although investigations by many authorsd on the properties of carbon cluster anions by mass spectrometry and photoelectron spectroscopy last more than a decade”1～3”, a general conclusion concerning the various features of the carbon clusters generated most commonly in laser vaporization/molecular beam sources has not yet been reached. In this Letter we report that the turn-over of the odd-even patter in relative abundance in the mass spectra of carbon clusters and the “manipulation” of the pattern can be realized in a controlled way by altering the vaporizing laser intensity, the backing pressure and the conductance of carries gas. As a general trend, the increase in intensity of the vaporizing laser and the reduction of the gas flow (case 1) favor the growth of the odd-numbered carbon cluster anions. In contrast, the decrease in laser intensity and the denser gas flow (case 2) make the even-numbered carbon cluster anions superior. Then an alternative odd-even pattern (odd ＞even, or even＞odd) of the carbon cluster anions in a TOF mass spectrum can be achieved. While the odd＞even pattern for even＞odd has been found from n = 6 to n = 130 and more, the oddeven pattern for odd＞even is not so special. However, such a pattern with odd＞even from n = 13 to, at least, n = 39, is possible. In the situation between the case 1 and case 2, a hybrid pattern exists as expected, showing that the intensity of the odd-numbered clusters are stronger in the range between n = 13～27 and the even-numbered clusters become dominant for n = 28 and larger. The present results may provide support of the necessity of further mass spectroscopic study of carbon cluster anions that would be important for a solid connection between the mass spectra and the geometric and electronic properties of the clusters being established.

机标关键词：Carbon Cluster、carbon clusters、laser intensity、mass spectra、electronic properties、spectroscopic study、gas flow、mass spectrum、the growth

所属期刊栏目：27

分类号：O56;O4

在线出版日期：2008-08-04（万方平台首次上网日期，不代表论文的发表时间）

页数：共5页

页码：191