Spin-rotation Energy Levels Research Articles

High sensitivity cavity ring down spectroscopy of the 3ν1+3ν2+ν3 band of NO2 near 7587 cm−1

The very weak 3ν1+3ν2+ν3 absorption band of the main isotopologue of nitrogen dioxide, 14N16O2, is investigated for the first time near 7587cm−1. The absorption spectrum was recorded by high sensitivity Continuous Wave-Cavity Ring Down Spectroscopy with a noise equivalent absorption of αmin≈1×10−10cm−1. 414 lines of the 3ν1+3ν2+ν3 band were assigned with rotational quantum numbers N and Ka as high as 32 and 6, respectively, what corresponds to 518 rotation–vibration transitions. The overall set of spin–rotation energy levels was modeled in the frame of the effective Hamiltonian approach and reproduced with an RMS of 6×10−3cm−1 for the (obs.–calc.) deviations. The effective Hamiltonian includes interactions with three nearby dark states – (350), (062) and (312) – in Coriolis interaction with the (331) bright state. Using a selected set of experimental line intensities and the fitted values of the vibration–rotation Hamiltonian parameters, the principal parameter in the dipole moment operator expansion is determined for the 3ν1+3ν2+ν3 band. With maximum line intensity on the order of 2.5×10−27cm/molecule at 296K, the 3ν1+3ν2+ν3 band is the weakest band of the NO2 molecule rovibrationnally assigned so far.

High sensitivity cavity ring down spectroscopy of NO2 between 7760 and 7917 cm−1

The very weak absorption spectrum of the main isotopologue of nitrogen dioxide, 14N16O2, is investigated for the first time between 7760 and 7917cm−1. The studied region corresponds to the highest energy range of the vibrational spectra of 14N16O2 investigated so far at high spectral resolution. The absorption spectra were recorded by very high sensitivity Continuous Wave-Cavity Ring Down Spectroscopy with a noise equivalent absorption of αmin≈5×10−11cm−1. The spectrum results from the superposition of the rovibrational transitions of the 2ν1+5ν2+ν3, 2ν1+ν2+3ν3 and 5ν1+ν3 bands at 7790.9, 7888.2 and 7904.3cm−1, respectively. The spectrum assignment and modeling were performed using the effective Hamiltonian approach, which involves altogether three bright – (2,5,1), (2,1,3) and (5,0,1) and three dark – (2,7,0), (2,3,2) and (5,2,0) states. As a result, 3020 rovibrational transitions were assigned including 51 extra lines of the 2ν1+3ν2+2ν3 and 5ν1+2ν3 bands. In this way, the overall set of 1494 spin-rotation energy levels were reproduced with an rms of 4.9×10−3cm−1 for the (obs.−calc) deviations, leading to the determination of 66 fitted parameters. The effective Hamiltonian for the {(5,2,0), (2,3,2), (2,7,0), (2,5,1), (2,1,3), (5,0,1)} interacting states takes into account both the spin–rotation interactions within each vibrational state and C-type Coriolis and anharmonic resonances between different vibrational states, according to symmetry considerations. Indeed for NO2 the (v,1v2±2,v3∓1)↔(v,1v2,v3) spin rotation energy levels are usually coupled through C-type Coriolis resonances, and accordingly the (2,7,0)↔(2,5,1)↔(2,3,2)↔(2,1,3) and (5,2,0)↔(5,0,1) interactions were included in the effective Hamiltonian model. Furthermore, these two blocks of interacting states are coupled by an additional C-type Coriolis and anharmonic resonances. Using the fitted values of the Hamiltonian parameters and the values of the 2ν1+5ν2+ν3, 2ν1+ν2+3ν3 and 5ν1+ν3 bands transition dipole moment operators determined from a fit of a selected set of experimental line intensities, a synthetic spectrum was generated for the entire investigated region and is provided as Supplementary material.

First high-resolution analysis of the 5ν3 band of nitrogen dioxide near 1.3 μm

The first high-resolution absorption spectrum of the 5ν3 band of the 14N16O2 molecule at 7766.071cm−1 was recorded by high sensitivity CW-Cavity Ring Down Spectroscopy between 7674 and 7795cm−1. The noise equivalent absorption of the recordings was αmin≈1×10−10cm−1. The assignments involve energy levels of the (0,0,5) vibrational state with rotational quantum numbers up to Ka=9 and N=47. The set of the spin–rotation energy levels were reproduced within their experimental uncertainty using a theoretical model, which takes explicitly into account the Coriolis interactions between the spin rotational levels of the (0,0,5) vibrational state and those of the (0,2,4) dark state together with the electron spin–rotation resonances within the (0,0,5) and (0,2,4) states. Precise values were determined for the (0,0,5) vibrational energy rotational, spin-rotational constants and for the (0,2,4)⇔(0,0,5) coupling constants. In addition the (0,2,4) rotational and spin-rotational constants were estimated. Using these parameters and the value of the transition dipole moment operator determined from a fit of a selection of experimental line intensities, the synthetic spectrum of the 5ν3 band was generated and is provided as Supplementary material.

First high-resolution analysis of the 4ν 1+ν 3 band of nitrogen dioxide near 1.5 μm

The high-resolution absorption spectrum of the 4ν 1+ν 3 band of the 14N 16O 2 molecule was recorded by CW-Cavity Ring Down Spectroscopy between 6575 and 6700 cm −1. The assignments involve energy levels of the (4,0,1) vibrational state with rotational quantum numbers up to K a=8 and N=48. A large majority of the spin-rotation energy levels were reproduced within their experimental uncertainty using a theoretical model which takes explicitly into account the Coriolis interactions between the spin-rotational levels of the (4,0,1) vibrational state and those of the (4,2,0) and of (0,9,0) dark states, the anharmonic interactions between the (4,2,0) and (0,9,0) states together with the electron spin-rotation resonances within the (4,0,1), (4,2,0) and (0,9,0) states. Precise vibrational energies, rotational, spin-rotational, and coupling constants were determined for the {(4,2,0), (0,9,0), (4,0,1)} triad of interacting states. Using these parameters and the value of the transition dipole-moment operator determined from a fit of a selection of experimental line intensities, the synthetic spectrum of the 4ν 1+ν 3 band was generated and is provided as Supplementary Material.

New high-resolution analysis of the ν1 + 3 ν3 band of nitrogen dioxide in the near infrared spectral region

The high-resolution Fourier-transform absorption spectrum of the 14N 16O 2 molecule was recorded in the near infrared 5200–6005 cm −1 spectral range. Starting from the results of a previous study [R.E. Blank, M.D. Olman, C.D. Hause, J. Mol. Spectrosc. 33 (1970) 109–118] a new analysis of the ν 1 + 3 ν 3 band located at 5984.705 cm −1 has been performed. The new assignments involve energy levels of the (1 0 3) vibrational state with rotational quantum numbers up to K a = 8 and N = 47. The spin–rotation energy levels were satisfactorily reproduced within their experimental uncertainty using a theoretical model which takes explicitly into account the Coriolis interactions between the spin-rotational levels of the (1 0 3) vibrational state and those of (1 2 2) and of (0 8 0), the anharmonic interactions between the (1 2 2) and (0 8 0) vibrational states together with the electron spin–rotation resonances within the (1 0 3), (1 2 2) and (0 8 0) vibrational states. As a consequence, precise vibrational energies, rotational, spin-rotational, and coupling constants were obtained for the triad {(1 2 2), (0 8 0), (1 0 3)} of interacting states of 14N 16O 2. Using these parameters a comprehensive list of line positions and of reliable line intensities was generated for the ν 1 + 3 ν 3 band of NO 2.

New high-resolution analysis of the { ν1 + ν3} band of the 15N 16O 2 isotopomer of nitrogen dioxide: Line positions and intensities

The high-resolution Fourier transform absorption spectrum of an isotopic sample of nitrogen dioxide, 15N 16O 2, was recorded in the 3.4 μm region. Starting from the results of a previous study [Y. Hamada, J. Mol. Struct. 242 (1991) 367–377] a new analysis of the ν 1 + ν 3 band located at 2858.7077 cm −1 has been performed. This new assignment concerns (1 0 1) energy levels involving rotational quantum numbers up to K a = 10 and N = 54. Using a theoretical model which accounts for both the electron spin-rotation resonances within each vibrational state and the Coriolis interactions between the (1 2 0) and (1 0 1) vibrational states, the spin-rotation energy levels of the (1 0 1) vibrational state could be reproduced within their experimental uncertainty. In this way, the precise vibrational energy, rotational, spin-rotation, and coupling constants were achieved for the {(1 2 0), (1 0 1)} interacting states of 15N 16O 2. Using these parameters and the transition moment operator which was obtained for the main isotopic species, 14N 16O 2, a comprehensive list of the line positions and intensities was generated for the ν 1 + ν 3 band of 15N 16O 2.

Observation of a new phosphorus-containing reactive intermediate: Electronic spectroscopy and excited-state dynamics of the HPBr free radical

The A (2)A(')-X (2)A(") electronic spectra of jet-cooled HPBr and DPBr have been obtained for the first time using the pulsed electric discharge technique with a precursor mixture of PBr(3) and H(2)/D(2). Laser-induced fluorescence and single vibronic level emission spectra gave the bending and P-Br stretching frequencies in the ground and excited states of both isotopomers. Rotational analyses of the HPBr and DPBr 0(0) (0) bands showed small spin splittings characteristic of a doublet-doublet transition of an asymmetric-top molecule. From the ground- and excited-state rotational constants, effective (r(0)) structures were derived with r(")(PH)=1.4307(86) A, r(")(PBr)=2.2021(9) A, and theta(")=95.2(8) degrees, and r(')(PH)=1.434(31) A, r(')(PBr)=2.1669(26) A, and theta(')=115.5(16) degrees . In a few favorable cases, further hyperfine splitting of the spin-rotation energy levels has been observed, due to the excited-state Fermi contact interaction of the unpaired electron with the spin magnetic moment of the (31)P nucleus, with a(F) (')=0.064(9) cm(-1) for HPBr. Fluorescence depletion spectroscopy and lifetime measurements indicate that higher vibrational levels of the A (2)A(') state are predissociated by a X (2)A(") dissociative continuum. CCSD(T)/aug-cc-pVTZ calculations predict that the most likely dissociation process is HPBr (X (2)A("))-->PH((3)Sigma(-))+Br((2)P(u)).

New High-Resolution Analysis of the ν3 Band of the 15N16O2 Isotopomer of Nitrogen Dioxide by Fourier Transform Spectroscopy

New high-resolution Fourier transform absorption spectra of an 15N16O2 isotopic sample of nitrogen dioxide were recorded at the University of Bremen in the 6.3-μm region. Starting from the results of a previous study [Y. Hamada, J. Mol. Struct. 242, 367–377 (1991)], a new and more extended analysis of the ν3 band located at 1582.1039 cm−1 has been performed. The spin–rotation energy levels were satisfactorily reproduced using a theoretical model which takes into account both the Coriolis interactions between the spin–rotation energy levels of the (001) vibrational state with those of the (020) and (100) states and the spin–rotation resonances within each of the NO2 vibrational states. Precise vibrational energies and rotational, spin–rotation, and coupling constants were obtained in this way for the first triad of 15N16O2 interacting states {(020), (100), (001)}. Finally, a comprehensive list of line positions and line intensities of the {ν1, 2ν2, ν3} interacting bands of 15N16O2 was generated, using for the line intensities the transition moment operators which were obtained previously for the main isotopic species.

New High-Resolution Analysis of the 3ν3 and 2ν1 + ν3 Bands of Nitrogen Dioxide (NO2) by Fourier Transform Spectroscopy

Using new high-resolution Fourier transform spectra recorded at the University of Denver in the 2-μm region, a new and more extended analysis of the 2ν1 + ν3 and 3ν3 bands of nitrogen dioxide, located at 4179.9374 and 4754.2039 cm−1, respectively, has been performed. The spin–rotation energy levels were satisfactorily reproduced using a theoretical model that takes into account both the Coriolis interactions between the spin–rotation energy levels of the (201) vibrational “bright” state with those of the (220) “dark” state. The interactions between the (003) bright state with the (022) dark state were similarly treated. The spin–rotation resonances within each of the NO2 vibrational states were also taken into account. The precise vibrational energies and the rotational, spin–rotational, and coupling constants were obtained for the two dyads {(220), (201)} and {(022), (003)} of the 14N16O2 interacting states. From the experimental line intensities of the 2ν1 + ν3 and 3ν3 bands, a determination of their vibrational transition moment constants was performed. A comprehensive list of line positions and line intensities of the {2ν1 + 2ν2, 2ν1 + ν3} and the {2ν2 + 2ν3, 3ν3} interacting bands of 14N16O2 was generated. In addition, assuming the harmonic approximation and using the Hamiltonian constants derived in this work and in previous studies (A. Perrin, J.-M. Flaud, A. Goldman, C. Camy-Peyret, W. J. Lafferty, Ph. Arcas, and C. P. Rinsland, J. Quant. Spectrosc. Radiat. Transfer 60, 839–850 (1998)), we have generated synthetic spectra for the {(022), (003)}–{(040), (021), (002)} hot bands at 6.3 μm and for the {(220), (201)}–{(100), (020), (001)} hot bands at 3.5 μm, which are in good agreement with the observed spectra.

The {ν1+ 2ν2, ν1+ ν3} Bands of14N16O2: Line Positions and Intensities; Line Intensities in the ν1+ ν2+ ν3− ν2Hot Band

High resolution Fourier transform absorption spectra of the14N16O2molecule recorded in the 2630–3510 cm−1spectral region have been analysed and lines of the ν1+ ν3band of this molecule have been assigned forKavalues ranging from 0 to 10 andNvalues up to 55. The spin–rotation energy levels were very satisfactorily reproduced using a theoretical model which takes explicitly into account both the Coriolis interaction between the spin–rotation levels of the (101) vibrational state and those of (120) and the spin–rotation resonances within (101) and (120). As a consequence, precise vibrational band centers and rotational, spin–rotation, and coupling constants were obtained for the {(120), (101))} interacting states of14N16O2. In addition, using a large set of individual ν1+ ν3experimental line intensities we have determined precisely the ν1+ ν3transition moment constants. Also from ν1+ ν2+ ν3− ν2line intensities measured in this work, the transition moment operator of the ν1+ ν2+ ν3− ν2hot band was found to be in agreement with the transition dipole moment of the corresponding cold band, namely, ν1+ ν3. Finally, a comprehensive list of line positions and intensities of the ν1+ ν3band of14N16O2has been generated at 3.4 μm.

The {2ν3, 4ν2, 2ν2+ ν3} and 2ν3− ν3Bands of14N16O2: Line Positions and Intensities

High resolution Fourier transform absorption spectra of the14N16O2molecule recorded in the 3000–3400 cm−1and 1520–1600 cm−1spectral regions have been analyzed. In this way lines of the 2ν3, 4ν2, 2ν2+ ν3, and 2ν3− ν3bands of14N16O2have been assigned withKavalues ranging from 0 to 8 andNvalues up to 60. The spin–rotation energy levels were very satisfactorily reproduced using a theoretical model which takes explicitly into account both the Coriolis interaction between the spin–rotation levels of the (021) vibrational state and those of (040) and of (002), and the spin–rotation resonances within (021), (040), and (002). As a consequence, precise vibrational band centers and rotational, spin–rotation, and coupling constants were obtained for the triad {(040), (002), (021)} of interacting states of14N16O2. In addition, using a large set of individual 2ν3, 4ν2, and 2ν2+ ν3experimental line intensities at 3.2 μm, we have determined precisely the 2ν2+ ν3and 2ν3transition moment constants of14N16O2. On the other hand, the transition moment constants of the 2ν3− ν3and 2ν2+ ν3− 2ν2bands were derived from those of the corresponding ν3cold band. Finally, a comprehensive list of line positions and intensities of the interacting 4ν2, 2ν3, 2ν2+ ν3, and 2ν3− ν3bands of14N16O2has been generated at 3.2 μm and 6.2 μm, respectively.

The ν2 + ν3 and ν2 + ν3 − ν2 Bands of 14N16O2: Line Positions and Intensities

High-resolution Fourier transform spectra recorded in the 2270-2400 cm−1 and 1520-1600 cm−1 spectral regions have been used to measure, up to very high N values, the positions of lines with Ka = 0-9 of the ν2 + ν3 and ν2 + ν3 − ν2 bands of 14N16O2 as well as their absolute intensities and a self broadening coefficient γ0 = 0.095 ± 0.032 cm−1 atm−1 (at 292 K). The spin-rotation energy levels were very satisfactorily reproduced using a theoretical model which explicitly takes into account both the Coriolis interaction between the spin-rotation levels of the (011) vibrational state and those of (030), and the spin-rotation resonances within (011) and (030). As a consequence, precise vibrational band centers and rotational, spin-rotation, and coupling constants were obtained for the diad {(030), (011)} of interacting states for 14N16O2. In addition, using a large set of individual ν2 + ν3 line intensities, we have determined precisely the ν2 + ν3 transition moments of 14N16O2. On the other hand, the transition moments of the ν2 + ν3 − ν2 and 3ν2 − ν2 bands were derived from those of the corresponding ν3 and 2ν2 cold bands. Finally, a comprehensive list of line positions and intensities of the interacting {ν2 + ν3, 3ν2} and {ν2 + ν3 − ν2, 3ν2 − ν2} bands of 14N16O2 has been generated at 4.2 and 6.2 μm, respectively.

The ν1, 2 ν2, and ν3 interacting bands of 14N 16O 2: Line positions and intensities

High-resolution Fourier transform spectra have been used in the 1200–1850 cm −1 spectral region to measure the positions of lines with K a = 0–15 for the ν 1 and ν 3 bands of 14N 16O 2, as well as lines with K a = 0, 1, 2, and 6 for the 2 ν 2 band up to very high N values. The spin-rotation energy levels were very satisfactorily reproduced using a theoretical model which takes explicitly into account both the Coriolis interactions between the spin-rotation levels of the (001) vibrational state with those of (100) and (020), and the spin-rotation resonances in each vibrational state. In this analysis, precise band centers and rotational, spin-rotation, and coupling constants were obtained for the triad {(100), (020), (001)} of interacting states for 14N 16O 2. In addition, using a large set of individual line intensities we have determined precisely the ν 1, 2 ν 2, and ν 3 transition moment operators of 14N 16O 2. Finally, a comprehensive list of line positions and intensities of the interacting ν 1, 2 ν 2, and ν 3 bands of 14N 16O 2 has been generated.