Hofstein Jason, Xu Haifeng, Sears Trevor, Johnson Philip
Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA.
J Phys Chem A. 2008 Feb 14;112(6):1195-201. doi: 10.1021/jp077367b. Epub 2008 Jan 19.
Pump-probe delayed ionization studies on phenylacetylene and benzonitrile in a supersonic beam reveal the production of a low-ionization-potential (approximately 5.7 eV) species lasting more than hundreds of microseconds after excitation to the S1 state. Excitation of the molecules was done with a frequency-doubled, Fourier transform-limited, pulse-amplified cw laser, and the rotationally resolved structure of the S1-S0 transition ensures that the excited molecules are monomers. Excited-state photoelectron spectroscopy shows that the long-lived species are formed during the light pulse but not by transfer from the fluorescing S1 population after the pulse, even though the S1 spectral signature is present in the long-lived action spectrum. This behavior differs greatly from that found in benzene and with most commonly held pictures of radiationless transitions in large molecules.
在超声束中对苯乙炔和苯甲腈进行泵浦-探测延迟电离研究，结果显示，激发到S1态后会产生一种低电离势（约5.7电子伏特）的物质，该物质在激发后可持续数百微秒以上。分子的激发是通过倍频、傅里叶变换极限、脉冲放大连续波激光器完成的，S1-S0跃迁的转动分辨结构确保了被激发分子为单体。激发态光电子能谱表明，长寿命物质是在光脉冲期间形成的，而非在脉冲后从荧光S1粒子群转移形成，尽管长寿命作用光谱中存在S1光谱特征。这种行为与在苯中发现的行为以及大多数关于大分子无辐射跃迁的常见观点有很大不同。
