Ring Down Research Articles

ROVIBRATIONAL LINE LISTS FOR NINE ISOTOPOLOGUES OF THE CO MOLECULE IN THE X 1 Σ + GROUND ELECTRONIC STATE

Extensive rovibrational line lists were computed for nine isotopologues of the CO molecule, namely, {sup 12}C{sup 16}O, {sup 12}C{sup 17}O, {sup 12}C{sup 18}O, {sup 13}C{sup 16}O, {sup 13}C{sup 17}O, {sup 13}C{sup 18}O, {sup 14}C{sup 16}O, {sup 14}C{sup 17}O, and {sup 14}C{sup 18}O in the ground electronic state with v ≤ 41, Δv ≤ 11, and J ≤ 150. The line intensity and position calculations were carried out using a newly determined piece-wise dipole moment function (DMF) in conjunction with the wavefunctions calculated from an experimentally determined potential energy function from Coxon and Hajigeorgiou. A direct-fit method that simultaneously fits all the reliable experimental rovibrational matrix elements has been used to construct the dipole moment function near equilibrium internuclear distance. In order to extend the amount and quality of input experimental parameters, new Cavity Ring Down Spectroscopy experiments were carried out to enable measurements of the lines in the 4-0 band with low uncertainty as well as the first measurements of lines in the 6-0 band. A new high-level ab initio DMF, derived from a finite field approach has been calculated to cover internuclear distances far from equilibrium. Accurate partition sums have been derived for temperatures up to 9000 K. In additionmore » to air- and self-induced broadening and shift parameters, those induced by CO{sub 2} and H{sub 2} are now provided for planetary applications. A complete set of broadening and shift parameters was calculated based on sophisticated extrapolation of high-quality measured data. The line lists, which follow HITRAN formalism, are provided as supplementary material.« less

パルス圧縮ATR-ステップスキャン時間分解-FT-IR/2D-IRによる高分子相互作用の可視化<br/>—慣性効果を利用したRing-downパルス圧縮波発生の検討—

これまで2D-IR法を併用したパルス圧縮ATR-動的赤外線形二色性(DIRLD)ステップスキャン–時間分解FT-IR分光法の開発検討を独自に行ってきた．今回，さらにフィルム試料とピエゾアクチュエータの間に硬度の高く高質量の超硬おもりブロックを挿入し，その慣性効果によりRing-downパルスを発生させる方法を検討した．その結果，高分子フィルムの粘弾性応答特性に応じた広い周波数分布を有する良好なマルチプレックス圧縮応力を発生させることが可能なことを見いだした．本手法を用いてポリエチレンテレフタレート(PET)フィルムの相互作用状態の解析を試みた．その結果，非晶質PETの各官能基の圧縮応答周波数分布は3.8 kHz付近であるのに対し，結晶化処理PETでは5 kHz付近の高周波数領域に分布が移動し，明瞭に両者の違いが観測された．フーリエ周波数別2D-IR解析による圧縮応答位相にも相違が検出され，PETの非晶・結晶化状態の違いを可視化することが可能であった．

Differential Detection Technique for Fiber Gas Sensor Based on Cavity Ring Down Spectroscopy

A new differential cavity ring-down spectroscopy (CRDS) detection technique is proposed. This technique features the wavelength differential detection by alternating two side bands generated by an optical single side band modulator. This is useful for detecting media with extremely narrow absorption spectra. The detection of carbon dioxide gas with a 1.572-μm wavelength is attempted at the wavelength difference of 0.16μm. The differential CRDS signal on the oscilloscope display is distinctly observed when the dioxide gas pressure exceeded 200Pa.

An empirical line list for methane in the 1.25 μm transparency window

The high resolution absorption spectrum of methane has been recorded at room temperature by high sensitivity Cavity Ring Down Spectroscopy between 7908.5 and 8345cm−1. The investigated spectral region corresponds to the high energy part of the 1.25μm transparency window where experimental measurements were missing. The extremely congested spectrum is mainly due to the superposition of weak bands of the triacontad in strong interaction. An empirical list of more than 12700 absorption features is built from a multiline fit of the spectrum.

The 4-0 band of carbon monoxide by high sensitivity Cavity Ring Down spectroscopy near 8200 cm−1

The room temperature spectrum of carbon monoxide in natural isotopic abundance is recorded by Cavity Ring Down Spectroscopy between 8094 and 8317cm−1. The investigated range covers the low frequency region of the third overtone band centered at 8414cm−1. The achieved sensitivity of the recordings corresponds to a noise equivalent absorption, αmin~5×10–12cm−1. 94 transitions are measured with intensity ranging between 3×10–27 and 1×10–30cm/molecule. They include the first observation of (i) high J lines of the P branch of the 4-0 band of 12C16O, (ii) the 4-0 band of 13C16O and 12C18O present in natural abundance in the sample (35 and 38 transitions, respectively), (iii) a few lines of the 4-0 band of 12C17O and of the 5-1 hot band of 12C16O. The spectroscopic parameters of the v=4 upper level of 13C16O and 12C18O are obtained from a fit of the measured line positions.The line positions reported with an accuracy of 5×10−4cm−1 and the derived line intensities are used for comparison to various theoretical line lists of carbon monoxide available in the literature. The agreement between the obtained experimental data and the most recent theoretical line lists available in the literature is discussed.

International comparison CCQM-K82: methane in air at ambient level (1800 to 2200) nmol/mol

The CCQM-K82 comparison was designed to evaluate the degrees of equivalence of NMI capabilities for methane in air primary reference mixtures in the range (1800 to 2200) nmol/mol. The balance gas for the standards was either scrubbed dry real air or synthetic air.CH4 in air standards have been produced by a number of laboratories for many years, with more recent developments focused on standards at atmospheric measurement concentrations and aimed at obtaining agreement between independently produced standards. A comparison of the differences in primary gas standards for methane in air was previously performed in 2003 (CCQM-P41 Greenhouse gases. 1 and 2) with a standard deviation of results around the reference value of 30 nmol/mol and 10 nmol/mol for a more limited set of standards. This can be contrasted with the level of agreement required from field laboratories routinely measuring atmospheric methane levels, set by Data Quality Objectives (DQO) established by the World Meteorological Organization (WMO) to reflect the scientifically desirable level of compatibility for CH4 measurements at the global scale, currently set at 2 nmol/mol (1 sigma).The measurements of this key comparison took place from May 2012 to June 2012.Eight laboratories took part in this comparison coordinated by the BIPM and NIST. Key comparison reference values were calculated based on Cavity Ring Down Spectroscopy Measurements performed at the BIPM, combined with participant's gravimetric values to identify a consistent set of standards. Regression analysis allowed predicted values for each standard to be calculated which acted as the KCRVs. In this comparison reported standard uncertainties by participants ranged from 0.50 nmol/mol to 2.4 nmol/mol and the uncertainties of individual KCRVs ranged from 0.68 nmol/mol to 0.71 nmol/mol.The standard deviation of the ensemble of standards about the KCRV value was 1.70 nmol/mol. This represents a greater than tenfold improvement in the level of compatibility of methane in air standards compared to that demonstrated in 2003. Further improvements in the compatibility of standards will require improved methods and uncertainties for the measurement of trace level methane in balance gases.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Three new bands of 18O16O18O by CW-CRDS between 6340 and 6800 cm−1

Three very weak bands of the 18O16O18O isotopologue of ozone have been detected by high sensitivity CW-Cavity Ring Down Spectroscopy between 6340 and 6800cm−1. They are vibrationally assigned as 2ν1+5ν3, ν1+4ν2+3ν3 and 3ν2+5ν3 and correspond to the highest frequency bands of this isotopologue detected so far. A total of 464, 318 and 194 transitions were rovibrationally assigned, respectively. The good agreement with theoretical values achieved for the derived band centres and rotational constants confirms the accuracy of the potential energy surface recently obtained via extensive ab initio calculations. A set of line intensities was measured and fitted to derive the first transition moment parameter of the three bands. The determined sets of effective Hamiltonian parameter and transition moment operators, as well as the experimental energy levels, were used to generate a complete list of 1526 transitions, provided as Supplementary materials. The calculated line-list allows generating a synthetic spectrum which reproduces satisfactorily the experimental spectrum.

Optical feedback frequency stabilized cavity ring-down spectroscopy.

We introduce optical feedback frequency stabilized cavity ring-down spectroscopy (OFFS-CRDS), a near-shot-noise-limited technique that combines kilohertz resolution with an absorption detection sensitivity of 5×10(-13) cm(-1) Hz(-1/2). Its distributed feedback laser source is stabilized to a highly stable V-shaped reference cavity by optical feedback and fine-tuned by means of single-sideband modulation. The stability of this narrow laser is transferred to a ring-down (RD) cavity using a new fibered Pound-Drever-Hall (PDH) locking scheme without a dedicated electro-optic phase modulator, yielding several hundred RD events per second. We demonstrate continuous coverage of more than 7 nm with a baseline noise of 5×10(-12) cm(-1) and a dynamic range spanning six decades. With its resonant intracavity light intensity on the order of 1 kW/cm2, the spectrometer was used for observing a Lamb dip in a transition of carbon dioxide involving four vibrational quanta. Saturating such a weak transition at 160 μW input power, OFFS-CRDS paves the way to Doppler-free molecular overtone spectroscopy for precision measurements of hyperfine structures and pressure shifts.

Photolysis of CH₃CHO at 248 nm: evidence of triple fragmentation from primary quantum yield of CH₃ and HCO radicals and H atoms.

Radical quantum yields have been measured following the 248 nm photolysis of acetaldehyde, CH3CHO. HCO radical and H atom yields have been quantified by time resolved continuous wave Cavity Ring Down Spectroscopy in the near infrared following their conversion to HO2 radicals by reaction with O2. The CH3 radical yield has been determined using the same technique following their conversion into CH3O2. Absolute yields have been deduced for HCO radicals and H atoms through fitting of time resolved HO2 profiles, obtained under various O2 concentrations, to a complex model, while the CH3 yield has been determined relative to the CH3 yield from 248 nm photolysis of CH3I. Time resolved HO2 profiles under very low O2 concentrations suggest that another unknown HO2 forming reaction path exists in this reaction system besides the conversion of HCO radicals and H atoms by reaction with O2. HO2 profiles can be well reproduced under a large range of experimental conditions with the following quantum yields: CH3CHO + hν(248nm) → CH3CHO*, CH3CHO* → CH3 + HCO ϕ(1a) = 0.125 ± 0.03, CH3CHO* → CH3 + H + CO ϕ(1e) = 0.205 ± 0.04, CH3CHO*[Formula: see text]CH3CO + HO2 ϕ(1f) = 0.07 ± 0.01. The CH3O2 quantum yield has been determined in separate experiments as ϕ(CH₃) = 0.33 ± 0.03 and is in excellent agreement with the CH3 yields derived from the HO2 measurements considering that the triple fragmentation (R1e) is an important reaction path in the 248 nm photolysis of CH3CHO. From arithmetic considerations taking into account the HO2 and CH3 measurements we deduce a remaining quantum yield for the molecular pathway: CH3CHO* → CH4 + CO ϕ(1b) = 0.6. All experiments can be consistently explained with absence of the formerly considered pathway: CH3CHO* → CH3CO + H ϕ(1c) = 0.

High sensitivity Cavity Ring Down spectroscopy of carbon dioxide in the 1.19–1.26 µm region

A Cavity Ring Down spectrometer using a fiber-connected External Cavity Diode Laser (ECDL) as light source has been developed to access the 1.26–1.19μm region. We present here the first application of this newly developed CW-CRDS spectrometer to the study of the highly sensitive spectrum of natural carbon dioxide between 7909 and 8370cm−1. The spectrum is dominated by the ν1+3ν3 dyad at 8192.55 and 8293.95cm−1 which forms the low energy border of the 1.2µm transparency window of importance for planetary applications. The achieved sensitivity (noise equivalent absorption, αmin, in the 10−10–10−11cm−1 range) allowed detection of numerous new transitions with intensity values down to 10−30cm/molecule, in particular hot bands reaching upper states with energy up to about 10,600cm−1.More than 3400 transitions belonging to the six major isotopologues of ‘natural’ carbon dioxide were assigned using the predictions of effective Hamiltonian (EH) models. A total of 2027, 442, 548, 303, 92 and 13 transitions belonging to 37, 9, 8, 4, 2 and 1 bands were rovibrationnally assigned for 12C16O2, 13C16O2, 16O12C18O, 16O12C17O, 16O13C18O and 16O13C17O, respectively. For comparison, only 14 12C16O2 absorption bands were previously known in the region (mostly from Venus spectra). Intensity values range between 2.1×10−30 and 2.4×10−24cm/molecule. All the identified bands correspond to the ΔP=11 series of transitions, where P=2V1+V2+3V3 is the polyad number (Vi are vibrational quantum numbers). The overall agreement of the EH predicted and measured line positions is very good (for instance, average and rms deviations of 0.64×10−3 and 3.8×10−3cm−1 for 12C16O2, respectively).The band-by-band analysis provided accurate spectroscopic parameters of 57 bands from a fit of the measured line positions. The global fits of the obtained intensity values of the ΔP=11 series of transitions were used to refine the corresponding set of effective dipole moment (EDM) parameters of the six studied isotopologues.The obtained results will help to improve the spectral line parameters of carbon dioxide in the most currently used spectroscopic databases. In particular, the calculated band intensities of a few weak hot bands are now in good agreement with the observations.

Electric quadrupole transitions and collision-induced absorption in the region of the first overtone band of H2 near 1.25 μm

The Q(1)–Q(4) electric quadrupole transitions of the first overtone band of H2 have been recorded for six pressure values up to 640Torr, by CW-Cavity Ring Down Spectroscopy near 8000cm−1. The noise equivalent absorption of the spectra is on the order of αmin≈5×10−12cm−1. Line intensities derived from a profile fit accounting for Dicke narrowing effects, range from 1.0×10−29 to 2.6×10−27cm/molecule for the Q(4) and Q(1) line, respectively. The claimed absolute uncertainty on the derived line positions and on the line strengths are of the order of 0.001cm−1 and 1%, respectively. The pressure line shifts of the four lines were derived allowing for an accurate determination of the position at zero pressure limit. The obtained positions and intensities agree within the experimental uncertainty with the most recent theoretical calculations including non-adiabatic, relativistic and quantum electrodynamical effects. The present frequency determinations confirm the high accuracy of these calculations. From the pressure dependence of the baseline of the CRDS spectra, the self continuum cross section of the collision induced absorption band of H2 is determined in the vicinity of the Q(1) line. The derived cross section is found in good agreement with recent theoretical values.

Imaging Artifacts During Transesophageal Echocardiography

Imaging Artifacts During Transesophageal Echocardiography

CW-Cavity Ring Down Spectroscopy of deuterated water in the 1.58 μm atmospheric transparency window

The spectrum of water vapour enriched in deuterium has been recorded by highly sensitive CW-Cavity Ring Down Spectroscopy in the 5855–6802cm−1 spectral region. The studied region includes the 1.58µm atmospheric transparency window of particular interest for remote sensing. More than 8000 absorption lines belonging to eight water isotopologues – H216O, H218O HD16O, D216O, HD18O, D218O, HD17O and D217O – were identified.The spectrum was assigned using both the IUPAC database of experimental transitions and energy levels, and accurate variational calculations. Overall, 1396 and 1277 experimental energy levels belonging to 18 and 16 upper vibrational states were retrieved for the HD16O and D216O species, respectively. 773 energy levels are newly derived. New experimental information concerns the high J (up to 20) and high Ka (up to 12) energy levels of the (101), (021), (040), (210), (120) states of HD16O and of the (111), (031), (210), (012), (130) states of D216O. While only a few energy levels were available, the rotational structure of the (130) and (220) states of HD16O could be analysed in detail. Rotational sublevels of the (140) state of D216O are reported for the first time. A detailed comparison of the derived energy levels with the values recommended by an IUPAC task group is presented. In particular, a significant improvement is evidenced for a number of quasi degenerate energy levels of HD16O. The obtained results are also discussed in relation with several recent studies.

An accurate and complete empirical line list for water vapor between 5850 and 7920 cm−1

An empirical line list has been constructed for “natural” water vapor at 296K in the 5850–7920cm−1 region. It was obtained by gathering separate line lists recently published on the basis of spectra recorded by high sensitivity Continuous Wave Cavity Ring Down Spectroscopy (CW-CRDS) of natural water, complemented with literature data for the strongest lines. The list includes 38,318 transitions of four major water isotopologues (H216O, H218O, H217O and HD16O) with an intensity cut-off of 1×10−29cm/molecule at 296K. The list is made mostly complete over the whole spectral region by including a large number of weak lines with positions calculated using experimentally determined energy levels and intensities obtained from variational calculations. In addition, we provide HD18O and HD17O lists in the same region for transitions with intensities larger than 1×10−29cm/molecule. The HD18O and HD17O lists (1972 lines in total) were obtained using empirical energy levels available in the literature and variational intensities.The global list (40,290 transitions) for water including the contribution of the six major isotopologues will be adopted for the next edition of the GEISA database in the region.The advantages and drawbacks of our list are discussed in comparison with the list provided for the same region in the 2012 edition of the HITRAN database. The direct comparison of the CRDS spectra to simulations based on the HITRAN list has revealed some insufficiencies which could easily be corrected: missing HDO lines, duplicated lines, inaccurate line positions or line intensities from variational calculations.

Rate constant of the reaction between CH3O2 and OH radicals

The rate constant of the reaction(R1)OH+CH3O2→productshas been measured at 294K by simultaneous coupling of Laser Induced Fluorescence (LIF) and cw-Cavity Ring Down Spectroscopy (cw-CDRS) to laser photolysis. OH radicals were generated by 248nm photolysis of either H2O2 or O3 in the presence of H2O, CH3O2 radicals were generated simultaneously by photolysis of CH3I and their absolute concentrations were obtained by cw-CRDS. OH decays were measured under excess CH3O2 concentrations and a very fast rate constant of k1=(2.8±1.4)×10−10cm3s−1 was found independent of pressure at 50 and 100Torr helium.

Set Up of an Automatic Water Quality Sampling System in Irrigation Agriculture

We have developed a high-resolution automatic sampling system for continuous in situ measurements of stable water isotopic composition and nitrogen solutes along with hydrological information. The system facilitates concurrent monitoring of a large number of water and nutrient fluxes (ground, surface, irrigation and rain water) in irrigated agriculture. For this purpose we couple an automatic sampling system with a Wavelength-Scanned Cavity Ring Down Spectrometry System (WS-CRDS) for stable water isotope analysis (δ2H and δ18O), a reagentless hyperspectral UV photometer (ProPS) for monitoring nitrate content and various water level sensors for hydrometric information. The automatic sampling system consists of different sampling stations equipped with pumps, a switch cabinet for valve and pump control and a computer operating the system. The complete system is operated via internet-based control software, allowing supervision from nearly anywhere. The system is currently set up at the International Rice Research Institute (Los Baños, The Philippines) in a diversified rice growing system to continuously monitor water and nutrient fluxes. Here we present the system's technical set-up and provide initial proof-of-concept with results for the isotopic composition of different water sources and nitrate values from the 2012 dry season.

High sensitivity Cavity Ring Down spectroscopy of 18O enriched carbon dioxide between 5850 and 7000 cm−1: Part II—Analysis and theoretical modeling of the 12C18O2, 13C18O2 and 16O13C18O spectra

More than 19000 transitions belonging to 11 isotopologues of carbon dioxide have been assigned in the room temperature absorption spectrum of highly 18O enriched carbon dioxide recorded by very high sensitivity CW-Cavity Ring Down spectroscopy between 5851 and 6990cm−1 (1.71–1.43μm). The line positions were determined with accuracy better than 1×10−3cm−1 while the absolute line intensities are reported with an uncertainty better than 10%. This second report is devoted to the analysis of the bands of three multiply substituted isotopologues: 12C18O2, 13C18O2 and 16O13C18O (828, 838 and 638 in short hand notation).On the basis of the predictions of effective Hamiltonian models, a total of 2870, 538 and 1375 transitions belonging to 59, 11 and 15 bands were rovibrationnally assigned for 828, 838 and 638, respectively. For comparison, only 11 bands were previously measured by Fourier Transform spectroscopy in the region, for the 828 species. All the identified bands correspond to a ΔP=9 variation of the polyad number (P=2V1+V2+3V3, where Vi are vibrational quantum numbers). The band-by-band analysis has allowed deriving accurate spectroscopic parameters of 81 bands from a fit of the measured line positions. A few resonance perturbations were identified. In particular, the 31113 and 51106 states of 638 belonging to different polyads (P=10 and P=11, respectively) are anharmonically coupled.Using the large set of newly measured line positions and those collected from the literature, the global modeling of the line positions within the effective Hamiltonian approach was performed and a new set of Hamiltonian parameters was obtained for each of the three considered isopotologues. Using a similar approach, the global fits of the obtained intensity values of the ΔP=9 series of transitions were used to derive the corresponding ΔP=9 effective dipole moment parameters of the three considered isotopologues. The obtained results will help to improve the quality of the spectral line parameters of the three considered minor isopotologues in the most currently used spectroscopic databases of carbon dioxide.

High sensitivity Cavity Ring Down spectroscopy of 18O enriched carbon dioxide between 5850 and 7000 cm−1: Part III–Analysis and theoretical modeling of the 12C17O2, 16O12C17O, 17O12C18O, 16O13C17O and 17O13C18O spectra

More than 19,700 transitions belonging to 11 isotopologues of carbon dioxide have been assigned in the room temperature absorption spectrum of highly 18O enriched carbon dioxide recorded by very high sensitivity CW-Cavity Ring Down spectroscopy between 5851 and 6990cm−1 (1.71–1.43μm). This third and last report is devoted to the analysis of the bands of five 17O containing isotopologues present at very low concentration in the studied spectra: 16O12C17O, 17O12C18O, 16O13C17O, 17O13C18O and 12C17O2 (627, 728, 637, 738 and 727 in short hand notation). On the basis of the predictions of effective Hamiltonian models, a total of 1759, 1786, 335, 273 and 551 transitions belonging to 24, 24, 5, 4 and 7 bands were rovibrationally assigned for 627, 728, 637, 738 and 727, respectively. For comparison, only five bands were previously measured in the region for the 728 species. All the identified bands belong to the ΔP=8 and 9 series of transitions, where P=2V1+V2+3V3 is the polyad number (Vi are vibrational quantum numbers). The band-by-band analysis has allowed deriving accurate spectroscopic parameters of 61 bands from a fit of the measured line positions. Two interpolyad resonance perturbations were identified.Using the newly measured line positions and those collected from the literature, the global modeling of the line positions within the effective Hamiltonian approach was performed and a new set of Hamiltonian parameters was obtained for the 17O12C18O, 16O13C17O and 17O13C18O isotopologues. For the five studied isotopologues, the effective dipole moment parameters of the ΔP=8 and 9 series were derived from a global fit of the measured line intensities. The obtained results will be used for the improvement of the quality of the line positions and intensities in the most currently used spectroscopic databases of carbon dioxide.

First detection of transitions in the second quadrupole overtone band of nitrogen near 1.44 μm by CW-CRDS with 6 × 10−13 cm−1 sensitivity

The extremely weak S(4) and S(6) electric quadrupole transitions of the 3-0 band of nitrogen have been detected by very high sensitivity CW-Cavity Ring Down spectroscopy near 6950cm−1. A noise equivalent absorption on the order of αmin∼6×10−13cm−1 was achieved by averaging several thousand 0.5cm−1 wide spectra recorded successively over several days. The studied 14N2 lines are among the weakest ever measured in the laboratory (intensity on the order of 1.5×10−31cm/molecule). The positions determined with a 0.002cm−1 uncertainty and the line intensities are compared with theoretical values included in the HITRAN2012 database.

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.