FOURIER TRANSFORM INFRARED SPECTRAL INVESTIGATION OF THE ν6\nu_6 BAND OF CYCLIC-C3_{3}H2_{2}

Author Institution: Department of Chemistry, Faculty of Science, Okayama University, 3-1-1; Tsushima-Naka, Okayama 700-8530, JAPANThe gas phase absorption spectrum of the $\nu_6$ band (out of plane in phase CH bend) of cyclopropenylidene (c-C$_3$H$_2$) has been observed using a high-resolution Fourier transform infrared spectrometer for the first time. The molecule was produced by microwave discharge through a flow of allene (25 mTorr) and Ar (30 mTorr) mixture inside a glass cell. The observed spectrum shows c-type ro-vibrational transitions in which the Q-branch lines (J values up to 34 and K$_a$ values up to 8) are strongly and distinctly stand out in the spectrum. A least squares fitting of a total of 357 tranitions (332 ro-vibrational transitions from this work and 25 transitions from the millimeter-wave spectrum with 10$^6$ times larger statistical weight) results in the determination of the rotational and centrifugal distortion constants in the upper state. The rotational constants agree with those determined by millimter-wave spectrum and thereby confirming the $\nu_6$ band ($\nu_{0} =$ 776.11729(17) cm$^{-1}$) of c-C$_3$H$_2$

FTIR Spectroscopy of NO₃: Perturbation Analysis of the ν₃+ν₄ State

High-resolution Fourier transform infrared spectra of the ¹⁵NO₃ ν₃+ν₄ and ν₃+ν₄–ν₄ bands were observed in the 1472 and 1112 cm^–1 regions. Compared with the case of ¹⁴N species, large effects of perturbations were recognized in many rotational levels of the ¹⁵NO₃ ν₃+ν₄ state, and it was found that the ν₂+2ν₄ state is responsible for the perturbation. Although a direct Coriolis interaction (Δν₂ = 1, Δν₃(or Δν₄)=1) is not present between these two vibrational levels, anharmonic terms including Φ₃₄₄ and Φ₄₄₄ mix ν₃+ν₄ and 3ν₄, ν₂+2ν₄, and ν₂+2ν₄ mixes with ν₂+ν₄ to produce Coriolis interaction between ν₃+ν₄ and ν₂+2ν₄. An analysis gave the energy difference of 7.274 cm^–1 between two levels, and interaction parameters were determined. Similar perturbation analysis was applied for the ¹⁴N species, and the previous ^pP­(<i>N</i>,<i>K</i>) assignment of the ν₃+ν₄ <i>A</i>′-ν₄ <i>E</i>′ band was changed for giving one A₂′ state. Spectral lines to another A₁′ state were not assigned because of weak intensity, which is explained by intensity anomaly through vibronic interaction, reflecting the transition moment of the <i>B̃</i>²<i>E</i>′–<i>X̃</i>²<i>A</i>₂^′ electronic band