The 2ν4 band spectrum of 14NO3 observed with infrared diode laser spectroscopy was analyzed with the Fourier transform (FT) spectrum in the 760 cm−1 region, including the Coriolis interaction between v4 = 2 and v2 = 1. The vibrational frequencies of v4 = 2, l = 0, and l = ±2 have been determined to be 752.4033(86) and 771.7941(81) cm−1, respectively. By considering the anharmonic interaction among the 2ν4, ν3, ν4, ν2, and ν2 + 3ν4 states, a relation among the cubic anharmonic constants was obtained as 0.452 Φ444ζ2,4 − 0.271 Φ344ζ2,3 = 127.7 cm−1. The ratio of transition moments μ(ν2)/μ(2ν4) was determined to be 0.3 from the perturbation analysis. The second strongest infrared band of 14NO3, ν3 + 2ν4, observed around 1927 cm−1 has been analyzed with the hot band ν3 + 2ν4 − ν4 by including the Coriolis interaction with the v2 = 1, v4 = 3 state. Similarly, the same band of 15NO3 was analyzed to give the band origin of 1897.9325(6) cm−1. The isotope shift 28.2 cm−1 for the ν3 + 2ν4 vibrational frequency is consistent with a predicted value of 27.3 cm−1. Although there are two A' states in v3 = 1, v4 = 2, only one A2' state has been assigned in the hot band, indicating that the other band has weak intensity. This fact and the strong intensity of the ν3 + 2ν4 band (l3 = ±1, l4 = 0) are understood as the effect of vibronic interaction. The first-order Coriolis coupling constant ζ of ν3 + 2ν4, l3 = 1, l4 = 0 is similar to those of the ν4 and ν3 + ν4 states, and it is concluded that the vibrational Coriolis coupling constant is nearly zero and the observed constants of ζ = −0.19 (14NO3) and ζ = −0.15 (15NO3) also originate from the effect of vibronic interaction.
- 2ν and ν + 2ν vibration
- IR spectroscopy
- Nitrate radical
- Vibronic interaction
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Physical and Theoretical Chemistry