## Abstract

The 2ν_{4} band spectrum of ^{14}NO_{3} 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 v_{4} = 2 and v_{2} = 1. The vibrational frequencies of v_{4} = 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 2ν_{4}, ν_{3}, ν_{4}, ν_{2}, and ν_{2} + 3ν_{4} states, a relation among the cubic anharmonic constants was obtained as 0.452 Φ_{444}ζ_{2,4} − 0.271 Φ_{344}ζ_{2,3} = 127.7 cm^{−1}. The ratio of transition moments μ(ν_{2})/μ(2ν_{4}) was determined to be 0.3 from the perturbation analysis. The second strongest infrared band of ^{14}NO_{3}, ν_{3} + 2ν_{4}, observed around 1927 cm^{−1} has been analyzed with the hot band ν_{3} + 2ν_{4} − ν_{4} by including the Coriolis interaction with the v_{2} = 1, v_{4} = 3 state. Similarly, the same band of ^{15}NO_{3} was analyzed to give the band origin of 1897.9325(6) cm^{−1}. The isotope shift 28.2 cm^{−1} for the ν_{3} + 2ν_{4} vibrational frequency is consistent with a predicted value of 27.3 cm^{−1}. Although there are two A' states in v_{3} = 1, v_{4} = 2, only one A_{2}' state has been assigned in the hot band, indicating that the other band has weak intensity. This fact and the strong intensity of the ν_{3} + 2ν_{4} band (l_{3} = ±1, l_{4} = 0) are understood as the effect of vibronic interaction. The first-order Coriolis coupling constant ζ of ν_{3} + 2ν_{4}, l_{3} = 1, l_{4} = 0 is similar to those of the ν_{4} and ν_{3} + ν_{4} states, and it is concluded that the vibrational Coriolis coupling constant is nearly zero and the observed constants of ζ = −0.19 (^{14}NO_{3}) and ζ = −0.15 (^{15}NO_{3}) also originate from the effect of vibronic interaction.

Original language | English |
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Pages (from-to) | 10-21 |

Number of pages | 12 |

Journal | Journal of Molecular Spectroscopy |

Volume | 334 |

DOIs | |

Publication status | Published - Apr 1 2017 |

## Keywords

- 2ν and ν + 2ν vibration
- IR spectroscopy
- Nitrate radical
- Vibronic interaction

## ASJC Scopus subject areas

- Atomic and Molecular Physics, and Optics
- Spectroscopy
- Physical and Theoretical Chemistry