Cross Sections For NO Research Articles

Theoretical Study of the Photochemical Mechanisms of the Electronic Quenching of NO(A2Σ+) with CH4, CH3OH, and CO2.

The electronic quenching of NO(A2Σ+) with molecular partners occurs through complex non-adiabatic dynamics that occurs on multiple coupled potential energy surfaces. Moreover, the propensity for NO(A2Σ+) electronic quenching depends heavily on the strength and nature of the intermolecular interactions between NO(A2Σ+) and the molecular partner. In this paper, we explore the electronic quenching mechanisms of three systems: NO(A2Σ+) + CH4, NO(A2Σ+) + CH3OH, and NO(A2Σ+) + CO2. Using EOM-EA-CCSD calculations, we rationalize the very low electronic quenching cross-section of NO(A2Σ+) + CH4 as well as the outcomes observed in previous NO + CH4 photodissociation studies. Our analysis of NO(A2Σ+) + CH3OH suggests that it will undergo facile electronic quenching mediated by reducing the intermolecular distance and significantly stretching the O-H bond of CH3OH. For NO(A2Σ+) + CO2, intermolecular attractions lead to a series of low-energy ON-OCO conformations in which the CO2 is significantly bent. For both the NO(A2Σ+) + CH3OH and NO(A2Σ+) + CO2 systems, we see evidence of the harpoon mechanism and low-energy conical intersections between NO(A2Σ+) + M and NO(X2Π) + M. Overall, this work provides the first detailed theoretical study on the NO(A2Σ+) + M potential energy surface of each of these systems and will inform future velocity map imaging experiments.

Pulsed-cavity ring down spectroscopic study of NO2 in 501–506 nm spectral region

Cavity ring-down spectroscopy (CRDS) is a highly sensitive laser absorption spectroscopic technique. In this paper, we report the pulsed CRDS study of nitrogen dioxide (NO 2 ) using an home-built CRDS set-up. Pulsed CRDS measurements of diluted NO 2 gas (0.091% in N 2 ) at various low pressures have been carried out in 501–506 nm spectral range. From the CRDS measurements, molecular spectral features of NO 2 at very low partial pressure, ∼10 mTorr (3.42 × 10 14 molecules/cm 3 ), was evidently observed. CRDS ring-down decay measurements carried out at wavelength of 504.76 nm for various molecular concentrations of NO 2 demonstrate a minimum detectable number density of NO 2 of 8.65 × 10 12 molecules/cm 3 , which would correspond to 350 ppbv under atmospheric condition. 40 ppbv of detection limit of NO 2 is estimated from the standard deviation (1σ) of ring-down decay time measurements at 504.76 nm wavelength. Absorption and integrated absorption cross section of NO 2 are also estimated.

Relaxation of NO+ by collision with para-H2 (j = 0)

ABSTRACT The first tentative detection of the nitrosylium ion (NO+) in the interstellar medium (ISM) was reported just a few years ago. The application of non-local thermal equilibrium models requires the knowledge of the collisional rate coefficients with the most common colliders in the ISM (e.g. He, H, H2, and e). The main goals of this paper are to study the collision of the NO+ molecule with para-H2 (j = 0) and report the rate coefficients for the lower rotational states of NO+. A large set of ab initio energies was computed at the CCSD(T)/aug-cc-pV5Z level of theory. A new potential energy surface averaged over the H2 orientations was then fitted using a reproducing kernel Hilbert space procedure. The state-to-state cross-sections of NO++para-H2 (j = 0) for the first 18 rotational levels were computed using the close-coupling method. The rotational rate coefficients of this system were compared with those for NO++He, and a different propensity rule was found. Furthermore, the hyperfine rate coefficients were also calculated using the infinite-order-sudden scaling procedure.

Photo-acoustic technology applied to ppb level NO<sub>2</sub> detection by using low power blue diode laser

Photo-acoustic technology based on a low power blue diode laser for measuring the ppb level NO<sub>2</sub> is presented in this paper. A low-cost NO<sub>2</sub> measurement system based on traditional photo-acoustic technology is established. The 405 nm blue diode laser with an external modulation is used as a light source. The central wavelength of the laser is 403.56 nm, the half-peak full width is 0.84 nm, and the power is 65.3 mW. The effective absorption cross section of NO<sub>2</sub> is obtained, and the interference of the water vapor and other trace gasisinvestigated. The resonant frequency is tested to be 1.35 kHz by frequency scanning fitting. An internally polished and coated poly tetra fluoroethylene aluminum cylindrical cavity is used as a photo-acoustic resonator (the inner diameter is 8 mm and the length is 120 mm). The influence factors caused by cavity parameters, optical windows and power supply are studied. The system is optimized to reduce background noise and improve signal-to-noise ratio. Then the noise signal is dropped to 0.02 <inline-formula><tex-math id="M4">\begin{document}${\text{μV}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20182262_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20182262_M4.png"/></alternatives></inline-formula>. An additional buffer chamber is integrated on the original buffer chamber to form a two-level buffer. The two-stage buffer structure significantly suppresses the effects of airflow noise and improves the system stability. The slope of the calibration curve of the system after linear fitting is 0.016 <inline-formula><tex-math id="M5">\begin{document}${\text{μV/ppb}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20182262_M5.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20182262_M5.png"/></alternatives></inline-formula>, and R<sup>2</sup> is 0.998. The NO<sub>2</sub> detection limit of system is 2 ppb (3<inline-formula><tex-math id="M6">\begin{document}$\sigma$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20182262_M6.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20182262_M6.png"/></alternatives></inline-formula>) with an average time of 60 s. To verify the results of the system, a diode laser cavity ring-down spectroscopy system (CRDS system, using a 409 nm the diode laser, with a system detection limit of 6.6 × 10<sup>–1</sup>) is used to measure ambient NO<sub>2</sub> simultaneouslyon Lake Dong-Pu in western Hefei, Anhui Province, China. During the experiment, the measured NO<sub>2</sub> concentration ranges from 8 to 30 ppb, with an average concentration of 20.8 ppb. The results of two systems have good consistency:alinear fitting slope of 0.94 ± 0.009, an intercept of 1.89 ± 0.18 and acorrelation coefficient of 0.87. The experimental results show that the system can realize the low-cost on-line detection of the ppb level NO<sub>2</sub>, and it can also be used for the real-time detection of NO<sub>2</sub> concentration field.

The role of near resonance electronic energy transfer on the collisional quenching of NO (A2Σ+) by C6H6 and C6F6 at low temperature

We present measurements of the collisional fluorescence quenching cross section of NO (A2Σ+) by benzene and hexafluorobenzene at a series of temperatures using a custom built slow flow cell and a pulsed de Laval nozzle test cell. The measurements show a deviation from the common harpoon mechanism of collisional fluorescence quenching, specifically the large quenching cross section of 147 Å2 at 300 K measured for benzene which is not predicted by the harpoon mechanism due to the low electron affinity of benzene (−1.5 eV). We speculate that the quenching of NO (A2Σ+) by benzene and hexafluorobenzene occurs through near resonance electronic energy transfer from the NO A-state to the A-state of the quencher via a pseudo-emission process. The predicted T−1/3 dependence of the cross section for this model is consistent with the experimental observations.

Angular distributions for the inelastic scattering of NO(X2Π) with O2(X3Σg-).

The inelastic scattering of NO(X2Π) by O2(X3Σg-) was studied at a mean collision energy of 550 cm-1 using velocity-map ion imaging. The initial quantum state of the NO(X2Π, v = 0, j = 0.5, Ω=0.5, 𝜖 = -1, f) molecule was selected using a hexapole electric field, and specific Λ-doublet levels of scattered NO were probed using (1+1') resonantly enhanced multiphoton ionization. A modified "onion-peeling" algorithm was employed to extract angular scattering information from the series of "pancaked," nested Newton spheres arising as a consequence of the rotational excitation of the molecular oxygen collision partner. The extracted differential cross sections for NO(X) f→f and f→e Λ-doublet resolved, spin-orbit conserving transitions, partially resolved in the oxygen co-product rotational quantum state, are reported, along with O2 fragment pair-correlated rotational state population. The inelastic scattering of NO with O2 is shown to share many similarities with the scattering of NO(X) with the rare gases. However, subtle differences in the angular distributions between the two collision partners are observed.

Comparative stereodynamics in molecule-atom and molecule-molecule rotational energy transfer: NO(A(2)Σ(+)) + He and D2.

We present a crossed molecular beam scattering study, using velocity-map ion-imaging detection, of state-to-state rotational energy transfer for NO(A(2)Σ(+)) in collisions with the kinematically identical colliders He and D2. We report differential cross sections and angle-resolved rotational angular momentum polarization moments for transfer of NO(A, v = 0, N = 0, j = 0.5) to NO(A, v = 0, N' = 3, 5-12) in collisions with He and D2 at respective average collision energies of 670 cm(-1) and 663 cm(-1). Quantum scattering calculations on a literature ab initio potential energy surface for NO(A)-He [J. Kłos et al., J. Chem. Phys. 129, 244303 (2008)] yield near-quantitative agreement with the experimental differential scattering cross sections and good agreement with the rotational polarization moments. This confirms that the Kłos et al. potential is accurate within the experimental collisional energy range. Comparison of the experimental results for NO(A) + D2 and He collisions provides information on the hitherto unknown NO(A)-D2 potential energy surface. The similarities in the measured scattering dynamics of NO(A) imply that the general form of the NO(A)-D2 potential must be similar to that calculated for NO(A)-He. A consistent trend for the rotational rainbow maximum in the differential cross sections for NO(A) + D2 to peak at more forward angles than those for NO(A) + He is consistent with the NO(A)-D2 potential being more anisotropic with respect to NO(A) orientation. No evidence is found in the experimental measurements for coincident rotational excitation of the D2, consistent with the potential having low anisotropy with respect to D2. The NO(A) + He polarization moments deviate systematically from the predictions of a hard-shell, kinematic-apse scattering model, with larger deviations as N' increases, which we attribute to the shallow gradient of the anisotropic repulsive NO(A)-He potential energy surface.

Collisional induced double electron loss of NO− and CH[formula omitted] anions below 10 keV energies

Double electron detachment cross sections for methane and nitric oxide negative ions passing through oxygen and nitrogen gas targets have been studied in the energy ranges of 2.0–10.0keV for CH4− and 4.0–10.0keV for NO−. The signal growth rate method was employed. Fragmentation was only observed for NO− anions colliding with both targets. In the case of CH4− anions no fragmentation was observed. The double electron detachment cross sections for methane ions is almost one order of magnitude larger than the one for nitric oxide ions. The fragmentation cross-sections for NO− is larger than the double electron detachment cross sections.

Low-temperature collisional quenching of NO A(2)Σ(+)(v' = 0) by NO(X(2)Π) and O2 between 34 and 109 K.

We present measurements of collisional fluorescence quenching cross sections of NO(A(2)Σ(+), v' = 0) by NO(X(2)Π) and O2 between 34 and 109 K using a pulsed converging-diverging nozzle gas expansion, extending the temperature range of previous measurements. The thermally averaged fluorescence quenching cross sections for both species show a monotonic increase as temperature decreases in this temperature range, consistent with earlier observations. These new measurements, however, allow discrimination between predictions obtained by extrapolating fits of previous data using different functional forms that show discrepancies exceeding 120% for NO and 160% for O2 at 34 K. The measured self-quenching cross section is 52.9 Å(2) near 112 K and increases to 64.1 Å(2) at 35 K, whereas the O2 fluorescence quenching cross section is 42.9 Å(2) at 109 K and increases to 58.3 Å(2) at 34 K. Global fits of the quenching cross section temperature dependence show that, when including our current measurements, the low temperature behavior of the quenching cross sections for NO and O2 is better described by a parameterization that accounts for the long-range interactions leading to the collisional deactivation via an inverse power law model.

Direct IR excitation in a fast ion beam: application to NO- photodetachment cross sections

BackgroundOptical access to a travelling ion packet is required in many ion beam experiments that study ion-photon interactions.MethodsAn approach is described for carrying out direct infrared excitation of a fast ion beam that uses an optical-quality reflective beam blocker to illuminate a counter propagating pulsed ion beam in a collinear configuration. This arrangement provides optical access along the axis of ion beam propagation by placing a mirror in the beam path at a 25 degree angle. The ion packet is bumped over the mirror, which is also used to block fast neutral particles produced during ion beam acceleration that also propagate along the beam path.ResultsThe efficiency of this setup is demonstrated in a photodetachment experiment on NO- anions, where a photoinduced depletion of up to 90% of the beam is achieved in a single laser shot. To demonstrate the application of this configuration, the relative photodetachment cross section for NO- has been measured in the range of 2800 – 7200 cm-1. The measured relative cross section shows a set of sharp peaks that are identified as vibrational autodetachment resonances.ConclusionThe new setup paves the way for future experiments where parent anionic species are vibrationally excited via direct infrared excitation first and undergo photodetachment/photodissociation in a subsequent step.PACS33.15.Ry; 33.80.Eh; 33.80.-b

Rotational alignment effects in NO(X) + Ar inelastic collisions: A theoretical study

Rotational angular momentum alignment effects in the rotational inelastic scattering of NO(X) with Ar have been investigated by means of close-coupled quantum mechanical, quasi-classical trajectory, and Monte Carlo hard shell scattering calculations. It has been shown that the hard shell nature of the interaction potential at a collision energy of Ecoll = 66 meV is primarily responsible for the rotational alignment of the NO(X) molecule after collision. By contrast, the alternating trend in the quantum mechanical parity resolved alignment parameters with change in rotational state Δj reflects differences in the differential cross sections for NO(X) parity conserving and changing collisions, rather than an underlying difference in the collision induced rotational alignment. This suggests that the rotational alignment and the differential cross sections are sensitive to rather different aspects of the scattering dynamics. The applicability of the kinematic apse model has also been tested and found to be in excellent agreement with exact quantum mechanical scattering theory provided the collision energy is in reasonable excess of the well depth of the NO(X)-Ar potential energy surface.

Absolute Photoionization Cross Section of the Ethyl Radical in the Range 8–11.5 eV: Synchrotron and Vacuum Ultraviolet Laser Measurements

The absolute photoionization cross section of C(2)H(5) has been measured at 10.54 eV using vacuum ultraviolet (VUV) laser photoionization. The C(2)H(5) radical was produced in situ using the rapid C(2)H(6) + F → C(2)H(5) + HF reaction. Its absolute photoionization cross section has been determined in two different ways: first using the C(2)H(5) + NO(2) → C(2)H(5)O + NO reaction in a fast flow reactor, and the known absolute photoionization cross section of NO. In a second experiment, it has been measured relative to the known absolute photoionization cross section of CH(3) as a reference by using the CH(4) + F → CH(3) + HF and C(2)H(6) + F → C(2)H(5) + HF reactions successively. Both methods gave similar results, the second one being more precise and yielding the value: σ(C(2)H(5))(ion) = (5.6 ± 1.4) Mb at 10.54 eV. This value is used to calibrate on an absolute scale the photoionization curve of C(2)H(5) produced in a pyrolytic source from the C(2)H(5)NO(2) precursor, and ionized by the VUV beam of the DESIRS beamline at SOLEIL synchrotron facility. In this latter experiment, a recently developed ion imaging technique is used to discriminate the direct photoionization process from dissociative ionization contributions to the C(2)H(5)(+) signal. The imaging technique applied on the photoelectron signal also allows a slow photoelectron spectrum with a 40 meV resolution to be extracted, indicating that photoionization around the adiabatic ionization threshold involves a complex vibrational overlap between the neutral and cationic ground states, as was previously observed in the literature. Comparison with earlier photoionization studies, in particular with the photoionization yield recorded by Ruscic et al. is also discussed.

A brief introduction and some background to the article JQSRT 1998;60:1025–31 and its companion

This note provides a short introduction, some background information and relevant history related to reprint of the article “Atmospheric remote-sensing reference data from GOME: Part 1. Temperature-dependent absorption cross-sections of NO 2 in the 231–794 nm range” (JQSRT 1998;60:1025–31). The article and its companion “Atmospheric remote-sensing reference data from GOME: 2. Temperature-dependent absorption cross sections of O 3 in the 231–794 nm range” (JQSRT 1999;61:509–17) provided timely and unique data sets of the absorption cross sections of Nitrogen dioxide, NO 2, and ozone, O 3. The reported absorption cross sections have a spectral resolution sufficient to distinguish the electronic vibrational and rotational features of NO 2 and O 3 and were made in the temperature range of relevance to the earth's atmosphere, viz. 200–300 K, over a wide spectral range. These species are two of the most important trace gases in earth's atmosphere, and play key roles in determining the chemistry and dynamics of the earth's atmosphere and the conditions at the earth's surface experienced by the biosphere. Whilst providing valuable information about the electronic states of NO 2 and O 3, these spectra were determined primarily for their exploitation in the retrieval of trace gases from measurements of solar back scattered radiation by ground based and space borne instrumentation. These yield the local and global amounts and distributions of NO 2 and O 3, thereby constraining our knowledge about atmospheric chemistry and dynamics and the impact of pollution from the local to the global scale. The measurement, publication and use of these spectral sets are among many important milestones in the development of atmospheric remote sensing.

Vacuum Ultraviolet Photoionization Mass Spectra and Cross-Sections for Volatile Organic Compounds at 10.5 eV

Vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS) has been applied to the detection of volatile organic compounds (VOCs), including aromatic, chlorinated, and oxygenated compounds. Photoionization mass spectra of 23 VOCs were measured using SPI-TOFMS at 10.5 eV (118 nm). The limits of detection of VOCs using SPI-TOFMS at 10.5 eV were estimated to be a few ppbv. The mass spectra of 20 VOCs exhibit only the parent ion and its isotopes' signals. The ionization processes of the VOCs were discussed on the basis of the reaction enthalpies predicted by the quantum chemical calculations. Absolute photoionization cross-sections for 23 VOCs, including 12 newly measured VOCs, at 10.5 eV were determined in comparison to the reported absolute photoionization cross-section of NO.

Exchange interaction effects in NO core-level photoionization cross-sections

The effect of the exchange interaction in the photoionization continuum is investigated, using N 1s photoionization of NO into the 1s−12π (1Π) and (3Π) final states as an example. The separation in energy of these two final states is 1.41 eV. Significant differences in their partial photoionization cross-sections are observed over a wide range of energies and cannot be accounted for by the different multiplicity of the states. We suggest that the deviation of the 3Π/1Π cross-section ratio from the statistical weighting at intermediate energies is dominated by the difference in the final-state potential experienced by the photoelectron and at asymptotically high energies by the multiplet-dependent amount of intensity going into multi-electron (shake-up) processes. Calculations underpinning this point are presented. We also show supporting measurements of the 3Π/1Π cross-section ratio for O 1s ionization and the absolute photoabsorption cross-section for NO over a wide energy range covering the core level region.

Temperature and Pressure Dependence of High-Resolution Air-Broadened Absorption Cross Sections of NO2(415−525 nm)

Cross sections of air-broadened NO_2 in the 415−525 nm region are reported. These are retrieved from 21 absorption spectra recorded at 0.060 cm^(-1) resolution with the McMath−Pierce Fourier Transform Spectrometer located on Kitt Peak in Arizona. The measurements are obtained for pressures (1−760 Torr) and temperatures (220−298 K) that are representative of typical tropospheric and stratospheric conditions. Two sigma uncertainty (95% confidence interval ≈ 2σ_(mean)) for the absolute absorption cross sections is below ±7% over the reported wavelength range. The average integrated intensity of all our data is 〈σ〉_(400-500 nm) = 4.53 × 10^(-17) cm^2 nm, which is within 0.2% of the averaged value from the recent literature. The wavelength (referred to vacuum) accuracy is 0.011 cm^(-1) (2.8 × 10^(-4) nm at 500 nm) and precision is 0.0022 cm^(-1) throughout the investigated wavelength range. In agreement with previous observations, high-resolution features in the NO_2 absorption spectrum display a strong pressure dependence with an effective pressure broadening parameter of 0.116 ± 0.003 cm^(-1)/atm (the rate of increase of Lorentzian half width at half-maximum with pressure). Temperature has a relatively minor effect on the shapes of individual high-resolution features, but it exerts a complex dependence on the relative line intensities. Absorption cross sections reported here represent the highest resolution data available over a substantial (>100 nm) wavelength range for quantitative analysis of NO_2 atmospheric column absorption spectra.

Single- and double-photoionization cross-sections of nitrogen dioxide (NO2) and ionic fragmentation of NO2+ and NO22+

Abstract Single- and double-photoionization processes of nitrogen dioxide (NO 2 ) have been studied in the photon energy region of 37–125 eV by use of time-of-flight mass spectrometry and the photoion–photoion coincidence method together with synchrotron radiation. The single- and double-photoionization cross-sections of NO 2 are determined. Ion branching ratios and the partial cross-sections for the individual ions, respectively, produced from the parent NO 2 + and NO 2 2+ ions are also determined separately at excitation energies where the molecular and dissociative single- and double-photoionization processes occur simultaneously. It was found that dissociation of the parent ions is dominant both in single and double photoionization. The thresholds for the O + + NO + and N + + O + dissociation channels of NO 2 2+ are at 35.0 ± 0.3 and 43.6 ± 0.3 eV, respectively. Kinetic energy releases in these two dissociation channels of NO 2 2+ have also been elucidated.

Measurements of molecular absorption spectra with the SCIAMACHY pre-flight model: instrument characterization and reference data for atmospheric remote-sensing in the 230–2380 nm region

Using the scanning imaging absorption spectrometer for atmospheric chartography (SCIAMACHY) pre-flight model satellite spectrometer, gas-phase absorption spectra of the most important atmospheric trace gases (O 3, NO 2, SO 2, O 2, OClO, H 2CO, H 2O, CO, CO 2, CH 4, and N 2O) have been measured in the 230–2380 nm range at medium spectral resolution and at several temperatures between 203 and 293 K. The spectra show high signal-to-noise ratio (between 200 up to a few thousands), high baseline stability (better than 10 −2) and an accurate wavelength calibration (better than 0.01 nm) and were scaled to absolute absorption cross-sections using previously published data. The results are important as reference data for atmospheric remote-sensing and physical chemistry. Amongst other results, the first measurements of the Wulf bands of O 3 up to their origin above 1000 nm were made at five different temperatures between 203 and 293 K, the first UV-Vis absorption cross-sections of NO 2 in gas-phase equilibrium at 203 K were recorded, and the ultraviolet absorption cross-sections of SO 2 were measured at five different temperatures between 203 and 296 K. In addition, the molecular absorption spectra were used to improve the wavelength calibration of the SCIAMACHY spectrometer and to characterize the instrumental line shape (ILS) and straylight properties of the instrument. It is demonstrated that laboratory measurements of molecular trace gas absorption spectra prior to launch are important for satellite instrument characterization and to validate and improve the spectroscopic database.

410-nm diode laser cavity ring-down spectroscopy for trace detection of NO 2

The detection of NO 2 at sub part per billion by volume (ppbv) concentrations has been demonstrated using a cavity ring-down spectrometer with a blue diode laser operating at wavelengths close to 410 nm. Measurements at peaks in the absorption spectrum at wavelengths of 410.4955 and 410.3533 nm demonstrate a minimum detectable number density of NO 2 of 9.8×10 9 molecules cm −3, which would correspond to 0.4 ppbv under atmospheric conditions in the lower troposphere. Additional experiments performed with a pulsed, tuneable dye laser system provide absorption cross-sections for NO 2 over the restricted wavelength ranges of 408.5–410.5 and 435.0–435.5 nm, but at a resolution of ∼ 0.06 cm −1 that is higher than previously reported and close to the Doppler broadening limit at 295 K. These spectra show considerably more structure than is evident in published Fourier transform (FT) spectra obtained at lower resolution, but yield cross-sections that are in quantitative agreement with the FT measurements.

Absorption cross-sections of NO 2: simulation of temperature and pressure effects

The measurements of the NO 2 absorption cross sections by several authors have been considered in order to derive its temperature and pressure dependences in the 13 200– 42 000 cm −1 spectral range. The temperature dependence is assumed to be linear in the temperature range investigated (217.0– 298.5 K ), whereas the influence of the total pressure is expressed as a temperature-dependent broadening coefficient. From measurements performed with mixtures of NO 2 in air and in N 2, values of γ air 0 (296 K) and γ N 2 0 (296 K) were found to be, respectively, 0.081±0.002 and 0.069±0.003 cm −1 atm −1 . The temperature coefficient n obtained in the present work is 0.8±0.1. The parameterization of the cross sections developed in this work can reproduce measured cross sections within 4%.