Vibration-rotation bands of 14N15N16O15N14N16O: 1.6–5.7 μm region

The infrared Fourier spectrum of 63 bands of ¹⁴N¹⁵N¹⁶O and of 69 bands of ¹⁵N¹⁴N¹⁶O have been measured and analyzed from 1750 to 6000 cm^?1. The rotational constants are given for 20 Σ, 11 Π, 7 Δ, and 3 Φ levels of ¹⁴N¹⁵N¹⁶O and 21 Σ, 14 Π, 8 Δ, and 5 Φ levels of ¹⁵N¹⁴N¹⁶O. Two bands of the previously unreported isotopic species ¹⁴N¹⁵N¹⁷O and ¹⁵N¹⁴N¹⁷O have been observed. Several local resonances are present in the levels 31^1c0 and 04⁰1 in ¹⁴N¹⁵N¹⁶O; 10⁰1, 06⁰0, 11^1d1, 12⁰1 in ¹⁵N¹⁴N¹⁶O. In both isotopes two “forbidden” Δ-Σ transitions are observed: 04^2c0-00⁰0 and 12^2c0-00⁰0.     

Vibration-rotation bands of 15N216O14N218O

The infrared spectrum of 64 bands of the isotopic species ¹⁵N₂¹⁶O of nitrous oxide and of 37 bands of ¹⁴N₂¹⁸O have been analyzed. The studied spectral range extends from 1750 to 6000 cm^?1 for ¹⁵N₂¹⁶O and from 1750 to 3100 cm^?1 for ¹⁴N₂¹⁸O. The effective rotational constants are given for 44 levels of ¹⁵N₂¹⁶O comprising 21Σ, 12Π, 7Δ, 4Φ levels and also for 29 levels of ¹⁴N₂¹⁸O comprising 13Σ, 7Π, 6Δ, 3Φ levels. Thirty-one levels (20Σ, 11Π) of the following isotopic species have also been studied: ¹⁵N₂¹⁷O, ¹⁵N₂¹⁸O, ¹⁴N¹⁵N¹⁸O, ¹⁵N¹⁴N¹⁸O, ¹⁴N₂¹⁷O. In ¹⁵N₂¹⁶O a local Coriolis resonance affects the 10⁰1 level. The “forbidden” Δ-Σ transition 12^2c0-00⁰0 is observed in the spectrum of ¹⁵N₂¹⁶O. The equilibrium values for the internuclear distances have been calculated.     

Microwave spectroscopy of OCS in highly excited vibrational states through energy transfer from N2

The efficient vibrational energy transfer between the first excited vibrational state of N₂ and the asymmetric stretching vibrational state of OCS has allowed the observation of many pure rotational lines in different vibrational states of OCS up to 4101 cm^?1: (00⁰1), (01¹1), (02^l1), (10⁰1), (00⁰2), (21¹0), (03^l0), (04^l0), and (05^l0). Accurate values of some rotational, centrifugal distortion and l-doubling constants are determined.     

Vibrational analysis of the A′1Π state of barium oxide using two isotopes

Barium vapor is reacted with N₂¹⁶O and N₂¹⁸O at 0.7 Torr to produce clearly distinguishable isotopic bands of BaO A′¹Π-X¹Σ in the wavelength region of 320–415 nm. The unique vibrational numbering is determined by measuring the isotopic shift in the bandheads between Ba¹⁶O and Ba¹⁸O. Spectroscopic constants for the A′¹Π state are determined from the present analysis to be ν₀₀ = 17 588 ± 15 cm^?1, ω_e = 442.45 ± 0.3 cm^?1, and ω_ex_e = 1.652 ± 0.009 cm^?1. Uncertainties represent three standard deviations.     

Vibration-rotation spectrum of N2O in the region of the lowest fundamental ν2

The high resolution infrared spectrum of N₂O in the region of ν₂ has been studied with a Fourier transform spectrometer at a resolution of (about) 0.005 cm^?1 and an accuracy of about ±0.00005 cm^?1. In addition to ν₂, “hot” bands associated with this band and the bending fundamental ν₂ of ¹⁵N¹⁴N¹⁶O and ¹⁴N¹⁵N¹⁶O were analyzed.     

High sensitivity CW-cavity ring down spectroscopy of N2O near 1.5 μm (III)

We present the third part of the investigation of the high sensitivity absorption spectrum of nitrous oxide by CW-Cavity Ring Down Spectroscopy near 1.5 μm. In the two first contributions (A. Liu, et al., J. Mol. Spectrosc. 244 (2007) 33-47 and A. Liu, et al., J. Mol. Spectrosc. 244 (2007) 48-62) devoted to the 5905-6833 cm⁻¹ region, more than 9000 line positions of five isotopologues (¹⁴N₂¹⁶O, ¹⁵N¹⁴N¹⁶O, ¹⁴N¹⁵N¹⁶O, ¹⁴N₂¹⁷O and ¹⁴N₂¹⁸O), were rovibrationally assigned to a total of 115 bands, most of them being newly detected. The achieved sensitivity (α_min∼3 × 10⁻¹⁰ cm⁻¹) allowed for the detection of lines with intensity weaker than 2 × 10⁻²⁹ cm/molecule. In this contribution, the investigated region was extended up to 7066 cm⁻¹. The analysis based on the predictions of the effective Hamiltonian model has allowed assigning about 1500 transitions to 17, 1, 2 and 1 bands of the ¹⁴N₂¹⁶O, ¹⁴N¹⁵N¹⁶O, ¹⁵N¹⁴N¹⁶O and ¹⁴N₂¹⁸O isotopologues, respectively. Eleven of these 21 bands are newly reported, while the observations of the transitions are extended to higher J values for most of the others. The band by band analysis has allowed reproducing the measured line positions within the experimental uncertainty (about 1 × 10⁻³ cm⁻¹) and determining the corresponding spectroscopic parameters. A detailed analysis of the rovibrational perturbations affecting three bands of ¹⁴N₂¹⁶O is presented.     

Line strengths and self-broadened linewidths of N2O in the 2-μm region: 2400-0000 and 0112-0000 transitions

The strenghths and self-broadened linewidths of the parallel 24⁰0-00⁰0 and perpendicular 01¹2-00⁰0 bands of N₂O have been measured with a precision better than 3%, using a deconvolution procedure. For both transitions, the coefficient of the vibration-rotation interaction polynomial, the values of the rotationless dipolar transition moment, and the band intensity have been calculated from the line strengths. For the total intensity the values found are S_00⁰0²⁴⁰⁰ = (1.325 ± 0.021) × 10^?2 cm^?2·atm^?1 and S_00⁰0⁰¹¹² = (1.209 ± 0.018) × 10^?2 cm^?2·atm^?1.     

Theoretical vibrational terms and rotational constants for the 15N substituted isotopologues of N2O calculated using normal hyperspherical coordinates

Variational calculations of the vibrational terms G_v and rotational constants B_v of the ¹⁴N¹⁵N¹⁶O, ¹⁵N¹⁴N¹⁶O and ¹⁵N¹⁵N¹⁶O isotopologues of nitrous oxide are carried out using normal hyperspherical coordinates. The Morse-cosine potential energy surface for N₂O previously determined by the authors by fitting to a set of experimental vibrational frequencies is employed. The G_v and B_v spectroscopic constants calculated for the ¹⁵N substituted isotopologues show an satisfactory agreement with those experimentally observed for a large number of vibrational bands of these isotopologues recently measured. Predicted calculated values of these spectroscopic constants for unobserved vibrational bands of the ¹⁵N substituted isotopologues are given in order to be of help in the identification and characterization of such bands, as a complement to the use of global effective Hamiltonians.     

High sensitivity CW-Cavity Ring Down Spectroscopy of N2O near 1.5 μm (II)

We present the second part of the investigation of the high sensitivity absorption spectrum of nitrous oxide by CW-Cavity Ring Down Spectroscopy near 1.5 μm. In a first paper [A.W. Liu, S. Kassi, P. Malara, D. Romanini, V.I. Perevalov, S.A. Tashkun, S.M. Hu, A. Campargue, J. Mol. Spectrosc. 244 (2007) 33-47] devoted to the 6000-6833 cm⁻¹ region, more than 6000 line positions of five isotopologues (¹⁴N₂¹⁶O, ¹⁵N¹⁴N¹⁶O, ¹⁴N¹⁵N¹⁶O, ¹⁴N₂¹⁷O, and ¹⁴N₂¹⁸O), were rovibrationally assigned to a total of 68 bands. The achieved noise equivalent absorption (α_min ∼ 2 × 10⁻¹⁰ cm⁻¹) allowed for the detection of lines with intensity weaker than 2 × 10⁻²⁹ cm/molecule. In this contribution, the investigated region was extended down to 5905 cm⁻¹ and additional recordings allowed accessing small spectral sections uncovered in our preceding recordings. A deeper analysis based on the predictions of the effective Hamiltonian model has allowed assigning a total of 3149 transitions and lowering the percentage of lines left unassigned from 51% to 28%. It led to the analysis of 35, 6, 7, and 6 bands for the ¹⁴N₂¹⁶O, ¹⁵N¹⁴N¹⁶O, ¹⁴N¹⁵N¹⁶O, and ¹⁴N₂¹⁸O isotopologues, respectively. Forty-two of these 54 bands are newly observed, while the rotational analysis of the twelve others is significantly extended and improved. Most of the bands were found unperturbed and their line positions could be reproduced within the experimental uncertainty (about 1 × 10⁻³ cm⁻¹). The corresponding spectroscopic parameters are reported. Local rovibrational perturbations induced by either intrapolyad or interpolyad couplings were found to affect five hot bands of ¹⁴N₂¹⁶O. Their detailed analysis is presented.     

Experimental and ab initio structure of BrN02

Abstract

The ν₂ fundamental bands of different isotopomers of BrN0₂ (⁷⁹Br¹⁵N¹⁶O₂, ⁸¹Br¹⁵N¹⁶O₂, ⁷⁹Br¹⁴N¹⁸O₂, and ⁷⁹Br¹⁴N¹⁶O¹⁸O) located around 13 µm were recorded using highresolution Fourier transform infrared spectrometry. More than 8000 lines of all these isotopomers were reproduced using a Watson-type A-reduced Hamiltonian with a rootmean-square deviation of better than 7×10^?4 cm^?1 for the four isotopomers. Rotational and centrifugal distortion constants for the ν₂=1 states as well as for the vibrational ground states of these isotopomers were determined. For the first time, an analysis of the ground-state rotational constants obtained in this study combined with the constants obtained in our previous work on the ν₂ bands of ⁷⁹Br¹⁴N¹⁶O₂, and ⁸¹Br¹⁴N¹⁶O₂, has allowed us to calculate the r_m, structure of nitryl bromide. The structural parameters obtained were r_m(Br–N)=2.0118(l6) Å, r_m(N–O)=l.l956(12) Å and α(O–N–O)=131.02(12)Å. A new ab initio structure of nitryl bromide calculated at the CCSD(T)/SDBaug-cc-pVQZ level of theory is presented and was found to be in fair agreement with the experimental structure.     

Laser Stark spectroscopy of FCN

Using a CO₂ laser, Stark shifted resonances have been measured for the CF stretching fundamental (ν₃) of FCN near 9.3 μm, and for two nearby “hot” bands. The band centers measured are 1076.492007 ± 0.000013 cm^?1 for 00⁰1-00⁰0, 1085.741046 ± 0.000050 cm^?1 for 01¹1-01¹0, and 1091.16222 ± 0.00015 cm^?1 for 02⁰1-02⁰0. The ground state dipole moment of FCN is found to be 2.1203 ± 0.0010 D and dipole moments are also given for the other states observed. Values are given for the rotational constant and l-doubling constant for the 01¹1 state.     

Lifetimes and transition frequencies of several singlet ungerade states in N2 between 106 000 and 109 000 cm

Using a narrow-band tunable XUV source, ultra-high resolution 1 XUV + 1 UV two-photon ionisation spectra were recorded of transitions to several singlet ungerade states in ¹⁴N₂ and ¹⁵N₂ in the range 106 000-109 000 cm⁻¹. The natural linewidths of the individual rotational spectral lines were determined and the resulting lifetimes were found to depend on vibrational level and for the c₃¹Π_u (v = 1) level also on isotope. Furthermore, accurate transition frequencies were determined and for several bands, lines near bandhead regions were resolved for the first time.     

Absolute frequency measurements of the 0002-0000, 2001-0000, and 1201-0000 bands of N2O by heterodyne spectroscopy

The absolute frequencies of 39 lines in the 00⁰2-00⁰0, 20⁰1-00⁰0, and 12⁰1-00⁰0 bands of N₂O in the range 4300–4800 cm^?1 have been measured by heterodyne frequency techniques. The lines were each measured in Doppler-limited absorption, with a color-center laser as a tunable probe of the N₂O and two stabilized CO₂ lasers as reference frequencies. New rovibrational constants have been fitted to these measurements. Tables of calculated transition frequencies are given, with estimated absolute uncertainties as small as 10^?4 cm^?1. The pressure shifts of four lines have been measured, and the values fall within the range of 0 to ?2 MHz/kPa (0 to ?0.2 MHz/Torr).     

Rotational analysis of the B-X band system of the SbO molecule

Rotational analyses of the two 0-0 bands of theB ²ΣX ²Π_reg system of SbO were carried out for the first time from spectrograms taken in the second order of a 21 ft. concave grating spectrograph having a dispersion of 1·25 Å/mm. The rotational constants of the ν=0 vibrational levels of the upper and lower states, and of the coupling constant A₀ of the lower²Π_reg state were deduced. These values are summarised below. v₀₀=25 334·93 cm^?1 B′₀=0·3190 cm^?1 B″₀=0·3490 cm^?1 A ₀=2276 cm^?1 r′₀=1·933 Å r″₀=1·848 Å.     

Sextic force field of nitrous oxide

The sextic force field in the curvilinear internal coordinates has been studied for the nitrous oxide molecule from the spectroscopic data of ¹⁴N₂¹⁶O, ¹⁴N¹⁵N¹⁶O, and ¹⁵N¹⁴N¹⁶O. The bands below 6600 cm⁻¹ have been used. The force constants in the internal coordinates are converted to those in dimensionless normal coordinates by two successive transformations. The vibration Hamiltonian matrix for each symmetry species of a given isotopic species has been constructed from the harmonic oscillator basis functions, and it is then diagonalized numerically to give the vibrational energy levels and the wavefunctions. The latter have been used for the evaluation of ratational constants. The least-squares refinement has been very successful in the present study, and it is shown that the general quartic force field supplemented by the quintic and sextic stretching diagonal force constants estimated from the Morse function, provided that the terms up to sextic are kept in the dimensionless normal coordinate space, well reproduces the spectroscopic constants such as the vibrational levels, rotational constants, l-type doubling constants, and centrifugal distortion constants. The spectroscopic constants of the isotopic molecules which are excluded from the refinement process are also in good agreement with the computed ones. The bond dissociation energies of the NN and NO bonds estimated from the present results have been critically examined.     

Heterodyne frequency measurements on N2O between 1257 and 1340 cm−1

Frequency measurements are given for the 00⁰1-00⁰0 and 01¹1-01¹0 bands of N₂O from 1257 to 1340 cm^?1. The measurements utilize heterodyne techniques by measuring small frequency differences between a tunable diode laser locked to the center of an N₂O absorption line and harmonic combinations of frequencies of radiation from two CO₂ Lamb-dip-stabilized lasers. The measurements are facilitated by the use of the CO laser as a transfer laser whose frequency is also measured. These measurements have been combined with other data to provide new band constants and frequency calibration tables for several band systems of N₂O in the following regions; 1215 to 1340, 1816 to 1930, and 2135 to 2268 cm^?1. A correction factor is also provided for existing calibration tables near 590 cm^?1.     

High resolution electronic study of ONO, ONO and ONO: A rovibronic survey covering 11 800-14 380 cm

The 11 800-14 380 cm⁻¹ frequency range has been scanned for rotationally resolved rovibronic transitions in the A²B₂-X²A₁ electronic band system of the symmetric (C_2v) ¹⁶O¹⁴N¹⁶O and ¹⁸O¹⁴N¹⁸O isotopologues and in the corresponding electronic band system of the asymmetric (C_s) ¹⁸O¹⁴N¹⁶O isotopologue. The rotational analysis—reflecting minor differences in mass—in combination with symmetry induced spectral differences allows an identification of 68 ¹⁶O¹⁴N¹⁶O vibronic levels, 26 ¹⁸O¹⁴N¹⁸O vibronic levels and 51 ¹⁸O¹⁴N¹⁶O vibronic levels. The bands are recorded using near infrared fluorescence spectroscopy and a piezo valve based pulsed molecular beam expansion of premixed ¹⁸O₂ and ¹⁴N¹⁶O in Ar. The majority of the observed bands is rotationally assigned and can be identified as transitions starting from the vibrational ground state of one of the isotopologues. Numerous hot bands have also been identified. A comparison of the overall spectroscopic features of C_2v vs. C_s symmetric species provides qualitative information on symmetry dependence of vibronic couplings.     

Absorption and emission spectra of matrix-isolated GeTe

Systems of broad bands have been observed in the absorption and laser-induced emission spectra of the GeTe molecule in solid argon and krypton matrices. Hitherto unreported electronic states have been characterized: a, ν₀₀ = 15 500 cm^?1; B, ν₀₀ = 20 070, ω_e = 190 cm^?1; C, ν₀₀ = 23 500, ω_e = 270 cm^?1. Higher energy states are also reported as well as an emission system in the red which is probably due to the Ge₂Te₂.     

High sensitivity CW-Cavity Ring Down Spectroscopy of N2O between 6950 and 7653 cm−1 (1.44–1.31 μm): I. Line positions

The absorption spectrum of nitrous oxide, N₂O, has been recorded by CW-Cavity Ring Down Spectroscopy between 6950 and 7653 cm^?1. The spectra were obtained at Doppler limited resolution using a CW-CRDS spectrometer based on a series of fibered DFB laser diodes. The typical noise equivalent absorption, in the order of α_min≈1×10^?10 cm^?1, allowed for the detection of lines with intensity as small as 1×10^–29 cm/molecule.The positions of 7203 lines of four isotopologues (¹⁴N₂¹⁶O, ¹⁴N¹⁵N¹⁶O, ¹⁵N¹⁴N¹⁶O and ¹⁴N₂¹⁸O) were measured with a typical accuracy of 1.0×10^?3 cm^?1. The transitions were rovibrationally assigned on the basis of the global effective Hamiltonian models developed for each isotopologue. The band by band analysis allowed for the determination of the rovibrational parameters of more than 95 bands, most of them being newly reported while new rotational transitions are measured for the others. The measured line positions of the main isotopologue are found to be in good agreement with the predictions of the effective Hamiltonian model but a few deviations up to 0.20 cm^?1 are observed. Local rovibrational perturbations were evidenced for several bands. The interaction mechanisms and the perturbers were univocally assigned on the basis of the effective Hamiltonian models.     

Absorption spectra of diatomic molybdenum nitride (MoN), molybdenum oxide (MoO), and molybdenum dimer (Mo2) molecules isolated in Ar,Ne, and Kr matrices

MoN and MoO molecules produced in a hollow cathode discharge have been trapped in Ne, Ar, and Kr matrices at 4.2 and 13 K and investigated by optical spectroscopy. Bands attributed to MoN were identified in the red and blue spectral regions and assigned by comparison with gas phase results to the A⁴π → X⁴Σ^? (a) and B⁴Σ → X⁴Σ^? (a) transitions, respectively. The ground state of Mo¹⁴N has been identified as ⁴Σ^? with ω_e = 1040 cm^?1 in an Ar matrix. Absorptions assigned to MoO in the red spectral region form the (0-0) and (1-0) bands of at least one electronic transition, but could not definitely be correlated with the gas phase results. The ground state vibrational frequency for Mo¹⁶O in an Ar matrix is 893.5 cm^?1. Additionally, Mo₂ absorptions centered at 19 305 cm^?1 were shown to be part of a vibrational progression with an average spacing of 181 cm^?1.