文摘
The excitation of the v3 = 1 (蟽g+ C鈭扖 stretch) and the v7 = 2 (蟺g2 C鈮鈭扖 bend) modes in the A2螤u electronic state of diacetylene cations results in Renner鈭扵eller (R鈭扵) and Fermi interactions. The 301 and 702 vibronic bands in the A2螤u鈭扻2螤g transition of HC4H+ have been measured with rotational resolution using cavity ringdown spectroscopy in a supersonic slit jet discharge. The analysis yields T00 = 20520.828(4) cm鈭?, B鈥?= 0.14047(2) cm鈭?, and A鈥?= 鈭?7.95(1) cm鈭? for the v3 = 1 and T00 = 20573.659(4) cm鈭?, B鈥?= 0.14018(3) cm鈭?, and A鈥?= 鈭?1.55(1) cm鈭? for the v7 = 2 level in the A2螤u electronic state. A vibronic analysis has been carried out taking into consideration the R鈭扵, spin鈭抩rbit, and Fermi resonance interactions between the 谓3 and 谓7 modes. The levels are fitted to the eigenvalues of an appropriate Hamiltonian matrix. This yields the vibrational frequencies 蠅3鈥?= 811.8 cm鈭? and 蠅7鈥?= 403.2 cm鈭?, Renner parameter 蔚7鈥?= 0.065, Fermi coefficients W1鈥?= 10.3 cm鈭? and W2鈥?= 5.1 cm鈭?, and spin鈭抩rbit interaction constant ASO鈥?= 鈭?1.1 cm鈭?. A corresponding R鈭扵 analysis has been carried out for the X2螤g ground state of HC4H+ using data available in the literature [Callomon, J. H. Can. J. Phys. 1956, 34, 1046]. This gives 蠅3鈥测€?= 956.2 cm鈭?, 蠅7鈥测€?= 435.4 cm鈭?, 蔚7鈥测€?= 0.028, W1鈥测€?= 7.2 cm鈭?, W2鈥测€?= 10.9 cm鈭?, and ASO鈥测€?= 鈭?3.3 cm鈭?.