Diode laser and Fourier transform infrared spectroscopy of jet-cooled nickel carbonyl

Abstract

Infrared absorption spectra of Ni(CO)4 in the region of its 510 band have been measured in supersonic jets using diode lasers and FTIR. The 510 band consisted of an intense Q branch and well-resolved P and R branches which clearly showed the effects of nuclear spin statistics. The analysis of 114 fundamental band transitions yielded the following effective parameters, which include small Coriolis effects (3σ uncertainties in parenthesis) ν̃0=2061.314 4(45) cm−1, B0=0.035 721 3(30) cm−1, B5=0.035 670 6(30) cm−1. The band center is blue-shifted by 3.5 cm−1 from the room temperature value due to the contribution of hot bands and higher-rotational distributions in the room temperature spectra. Weaker features near the 510 Q branch in the diode laser spectra are assigned to the Q branches of two hot bands. Their spectra, optimized using higher concentrations of Ni(CO)4 in He or Ar seed gas, were analyzed to give rotation, vibration–rotation and anharmonicity parameters. The effective hot band centers are: ν̃0(510411) =2060.996 4(50) cm−1, ν̃0(510811) =2061.114 8(48) cm−1.