Observation and Analysis of N2O Rotation–Vibration Spectra

The linear molecule N2O is presented as an alternative gas-phase species for the ubiquitous undergraduate physical chemistry rotation–vibration spectroscopy experiment. Utilizing a 0.5 cm−1 resolution teaching grade FTIR spectrometer, 15 vibrational bands, corresponding to 1229 rotation–vibration transitions, have been observed in the region 5000–500 cm−1. The large quantity of observed data presents the opportunity to assign each of 15 students, or groups, a unique band to analyze independently. The data analysis of each band is straightforward, involving P- and R- branch transition-energy expressions similar to those used in the analysis of traditional diatomic molecules such as HCl and CO, and result in the determination of a band origin and B rotational constants. Spectroscopic constants of independent band analyses can be pooled to determine anharmonicity and vibration–rotation constants and prepare a vibrational energy-level diagram involving the 15 observed states.