Redetermination of some of the spectroscopic constants of the electronic ground state of di‐Nitrogen ¹⁴N₂, ¹⁴N¹⁵N and ¹⁵N₂ using coherent anti‐stokes Raman spectroscopy

Abstract

Calibrated coherent anti-Stokes Raman (CARS) spectra have been recorded for the resolved Q branches of the vibrational fundamentals and first hot bands of I4N,, l4N''N and 15N, at a temperature of 1200 K. The spectra show a convolved linewidth of 0.13 cm-', and have been used to derive new values of spectroscopic constants, for the species observed, with specific reference to the position of the Q branch lines where J > 20 for u = 1-0, and J = 0-30 for u = 2-1. The critical overlap region of the fundamental and the hot band may now be computer simulated with confidence, which should be of considerable help in combustor thermometry using CARS.

High-Resolution Coherent Raman Spectra of Vibrationally Excited14N2and15N2

“…(22), rather than the constrained parameters implied by Dunham's with differences deduced from the only other Raman data, from measurements of Q branches by Bendtsen (5) and by notation (23,24). In the latter case, for example, one conGilson et al (6) (3,8,9,11) for 14 N 2 terms D 10 and D 20 were found to be statistically significant are hindered by the variation in number of fitted parameters and are listed in Table 3. Compared to the two separate fits, in the various fits; in general the major Y kl values are consis-the combined analysis decreased the number of parameters tent but our decreased estimated standard errors imply much from 18 to 12, the values of which can be used for the increased precision.…”

“…The Q-branch vacuum wavenumber input data sets and uncertainties specified above. The deduced parameters were R e and coefficients c j , 0 £ j £ 6 values of Tables 1 and 2 Table 3; experimental values are taken from this work, from Gilson et al (6), and from Bendtsen ( 5). Numbers in parentheses indicate the range of J for each Q branch.…”

“…Gilson et al (6) measured coherent anti-Stokes Raman scattering (CARS) spectra at a resolution of 0.15 cm 01 of Q Although contemporary infrared spectra of polar diatomic branches in the bands 1 R 0 and 2 R 1 of 14 N 2 in a vessel molecular species can yield abundant measurements of at 1200 K; these measurements were not calibrated absowavenumbers of vibration-rotational transitions with precilutely but were normalized to Bendtsen's data (5). Measuresion typically about 0.001 cm 01 , or even much better ments on heated 14 N 2 were made also by Lavorel and co-(Ç10 06 cm 01 ) in exceptional cases, the corresponding tranworkers (7,8) in the form of stimulated Raman spectra but sition energies of nonpolar molecules are less well estabat a resolution and absolute uncertainty of wavenumbers of lished.…”

High‐pressure pure rotational CARS: comparison of temperature measurements with O2, N2 and synthetic air

“…1) even for measurements at high pressures. 2,3 For this, also the spectroscopic constants of N 2 have been determined accurately 4,5 and the collisional parameters of N 2 have been studied extensively (see, e.g., . Nevertheless, there are applications such as oxygen-fuelled combustion in which N 2 is not present to a significant extent.…”

Accurate spectroscopic constants of nitrogen determined from stimulated Raman spectra of the fundamental and first hot bands

“…6 In Ref. 2, the CARS spectra of the fundamental and first hot bands of nitrogen were employed to redetermine some constants. Two studies have been devoted to the u = 0 -+ 1 transition by using a highaccuracy absolute wavenumber calibration with the help of stimulated Raman3 or quadrupolar absorption6 spectroscopy.…”