Jacovella U, Merkt F
Laboratorium für Physikalische Chemie, ETH Zürich, CH-8093 Zurich, Switzerland.
Phys Chem Chem Phys. 2017 Aug 30;19(34):23524-23531. doi: 10.1039/c7cp04759b.
The photoelectron spectra of the XΠ ← X Σ photoionizing transition of diacetylene (HCCCCH) and d2-diacetylene (DCCCCD) have been recorded at high resolution using the technique of pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectroscopy. The partially resolved rotational structure of the origin band of the spectra of HCCCCH and DCCCCD has enabled the determination of the adiabatic ionization energies of HCCCCH [E = 82072.2(5) cm] and DCCCCD [E = 82090.0(10) cm] and of the spin-orbit coupling constant [A = -31.1(4) cm] of the ground vibronic state of HCCCCH, which is smaller than the value of -33.3 cm commonly used since the work of Callomon (J. H. Callomon, Can. J. Phys., 1956, 34, 1046). Several excited vibrational levels of HCCCCH and DCCCCD, including some affected by the Renner-Teller effect and Fermi interactions, have been observed and the fundamental wavenumber of the mode ν has been determined in both HCCCCH (200.0(10) cm) and DCCCCD (192.6(20) cm). Possible assignments for several of these levels are discussed and deficiencies in the current understanding of the energy-level structure of the radical cation of diacetylene are pointed at.
利用脉冲场电离零动能（PFI-ZEKE）光电子能谱技术，高分辨率记录了丁二炔（HCCCCH）和d2-丁二炔（DCCCCD）的XΠ←XΣ光电离跃迁的光电子能谱。HCCCCH和DCCCCD光谱起始带的部分分辨转动结构，使得能够确定HCCCCH [E = 82072.2(5) cm]和DCCCCD [E = 82090.0(10) cm]的绝热电离能，以及HCCCCH基振动态的自旋-轨道耦合常数[A = -31.1(4) cm]，该值小于自卡洛蒙（J. H. Callomon，《加拿大物理学杂志》，1956年，34卷，1046页）的工作以来常用的-33.3 cm的值。观察到了HCCCCH和DCCCCD的几个激发振动态，包括一些受伦纳-泰勒效应和费米相互作用影响的态，并确定了HCCCCH（200.0(10) cm）和DCCCCD（192.6(20) cm）中模式ν的基波数。讨论了其中几个能级的可能归属，并指出了目前对丁二炔自由基阳离子能级结构理解中的不足。
