Excited NO Molecules Research Articles

Effect of exchange reactions and NO vibrational excitation on shock-heated air component flows

Shock-heated flows of air components are studied using the state-to-state approach taking into account coupled vibrational energy transitions and state-specific chemical reactions. Effects of exchange reactions and vibrational excitation of NO molecules on the fluid-dynamic variables and vibrational distributions are evaluated; the results are compared to experimental data and direct simulations Monte Carlo; satisfactory agreement is obtained. It is shown that the effects are opposite in mixtures with and without initial admixture of NO. Whereas in NO/N2/Ar mixture the effect of NO vibrational excitation is important, in air it is negligible. Exchange reactions in air are more important than in NO/N2/Ar mixture.

Infrared Glow of Nitric Oxide in Earth’s Middle Atmosphere during GLE Events of the 23rd Solar Cycle

The article considers the production kinetics of vibrationally excited NO(X2Π, 0) molecules at heights of Earth’s middle atmosphere during the precipitation of high-energy protons. The intensity profiles of the luminescence of the infrared bands of nitric oxide at 5.3 and 2.7 μm were calculated for precipitation of high-energy protons into Earth’s atmosphere during the events GLE65, GLE67, GLE69, and GLE70 of the 23rd solar cycle. Calculations have shown that the highest integral luminescence intensity values of the 5.3 and 2.7 μm bands were obtained for GLE69: 5.7 and 0.18 kR (kilorayleighs), respectively. Comparison of the calculation results for the 5.3 µm band during the GLE69 event with experimental data obtained from the TIMED spacecraft on January 20, 2005, showed that the calculation results were overestimated by a factor of 2.

Vibrational Kinetics of NO and N2 in the Earth's Middle Atmosphere During GLE69 on January 20, 2005

AbstractThe mechanisms of the production of vibrationally excited NO and N2 molecules at the altitudes of the middle atmosphere of the Earth during high‐energetic proton precipitation on 20 January 2005 are considered. The study of vibrational populations N2(X1Σg+,v′ > 0) during high‐energetic proton precipitation has shown different principal mechanisms in the N2(X1Σg+,v′ > 0) excitation. First, the excitation by secondary electrons is principal for vibrational levels v′ = 1−10. Second, it is obtained that intramolecular electron energy transfer process in N2(A3Σu+)+N2 collisions dominates in vibrational excitation of high vibrational levels v′ = 20−30. It is shown that the chemical reaction of metastable atomic nitrogen with molecular oxygen is the main production mechanism of vibrationally excited NO(X2Π,v > 0) and of the radiation of 5.3 and 2.7 μm infrared emissions at these altitudes. The calculated intensities of the 5.3 μm emission are compared with experimental data from SABER instrument on TIMED spacecraft received at the time of the proton precipitation. The role of VV′‐processes in the radiation of 5.3 μm infrared emission is discussed.

Direct imaging of the hyperfine depolarization in electronically excited NO molecules

Using pump-probe imaging, the authors study the depolarization dynamics of electronically excited NO molecules by tracking the angular distribution of the molecular axis. They show an evolution from alignment to antialignment, a manifestation of rotational angular momentum depolarization by the hyperfine interaction with the N nuclear spin.

Cold collisions of hot molecules.

In this Perspective, we review our recent work on rotationally inelastic collisions of highly vibrationally excited NO molecules prepared in single rotational and parity levels at v = 10 using stimulated emission pumping (SEP). This state preparation is employed in a recently developed crossed molecular beam apparatus where two nearly copropagating molecular beams achieve an intersection angle of 4° at the interaction region. This near-copropagating beam geometry of the molecular beams permits very wide tuning of the collision energy, from far above room temperature down to 2 K where we test the theoretical treatment of the attractive part of the potentials and the difference potential for the first time. We have obtained differential cross sections for state-to-state collisions of NO (v = 10) with Ar and Ne in both spin-orbit manifolds using velocity map imaging. Overall good agreement of the experimental results was seen with quantum mechanical close-coupling calculations done on both coupled-cluster and multi-reference configuration interaction potential energy surfaces. Probing cold collisions of NO carrying ∼2 eV of vibrational excitation allows us to test state-of-the-art theory in this extreme nonequilibrium regime.

Vibrational Relaxation of Highly Vibrationally Excited Molecules Scattered from Au(111): Role of the Dissociation Barrier

Energy transfer during molecular collisions at a metal surface represents a sensitive probe of the molecule–surface interaction potential. Here, via molecular dynamics calculations on several first-principles neural network potentials, we find that the vibrational energy transfer dynamics of highly vibrationally excited NO and CO molecules scattered from Au(111) are strongly correlated with their respective potential energy landscapes in the vicinity of the dissociation barrier. Our results not only reproduce the observed significantly less vibrational relaxation of CO (vi = 17) than NO (vi = 16) scattered from Au(111) and attribute it to the different dissociation barriers in the two systems, but also show a dramatic change of dynamics due to a minor adjustment of the energy landscape near the barrier in the CO case. We find that the BEEF-vdW density functional based potential largely overestimates the vibrational relaxation of CO (vi = 17) even in the absence of any nonadiabatic energy loss, despite its good description for CO adsorption on Au(111). We also discuss the possibility of integrating the validated adiabatic potential with first-principles determined diabatic states towards a more complete description of the non-adiabatic energy transfer in these benchmark systems.

Dissociative electron attachment cross sections for ro-vibrationally excited NO molecule and N − anion formation

Motivated by the huge need for data for non-equilibrium plasma modeling, a theoretical investigation of dissociative electron attachment to the NO molecule is performed. The calculations presented here are based on the local-complex-potential approach, taking into account five NO− resonances. Three specific channels of the process are studied, including the production of excited nitrogen atoms N(2D) and of its anions N−. Interpretation of the existing experimental data and their comparison with our theoretical result are given. A full set of ro-vibrationally-resolved cross sections and the corresponding rate coefficients are reported. In particular, a relatively large cross sections for N− ion formation at low energy of the incident electron and for vibrationally excited NO target are predicted. Finally, molecular rotation effects are discussed.

Models validation and code profiling in state-to-state simulations of shock heated air flows

The objective of this study is to examine various combinations of vibration-chemical coupling models in high-temperature air and oxygen flows behind shock waves. Simulations are carried out in the frame of the state-to-state approach for detailed vibrational and chemical kinetics in the Euler approximation. Great variety of state-resolved models for the rate coefficients of vibrational energy transitions and chemical reactions are assessed and validated against experimental data; among them are first-order perturbation (SSH) and forced harmonic oscillator (FHO) models; well-known Marrone–Treanor dissociation model with parameters either obtained empirically or by fitting quasiclassical trajectory calculations; new models for state-specific Zeldovich reactions. To validate the models, the results of numerical flow simulations are compared with experimental investigations in a wide range of initial mixture compositions and shock wave velocities. Among numerous model variants, a few models providing the best agreement with the experimental data on the vibrational temperature in oxygen flows and measured NO radiation in air flows are recommended for different sets of free stream conditions. The impact of NO excited states produced in Zeldovich reactions is evaluated; it is shown that neglecting the vibrational excitation of NO molecules may lead to significantly underpredicted maximum of NO number density. In the framework of the code performance study, Matlab and Fortran implementations were compared, the most significant bottlenecks procedures were identified by profiling analysis, and remarkable speed-up was achieved by code optimisation.

A versatile molecular beam apparatus for cold/ultracold collisions

We have developed an apparatus capable of performing intrabeam and near-copropagating beam scattering experiments at collision energies from room temperature to below 1 K where interesting quantum phenomena can be observed. A detailed description of the major components of the apparatus, single and dual molecular beam valves, high speed chopper, and the discharge source, is presented. With the intrabeam scattering setup, a novel dual-slit chopper permits collision energies down to millikelvins with a collision energy spread of 20%. With the near-copropagating beam configuration, state-to-state differential cross sections for rotationally inelastic collisions of highly vibrationally excited NO molecules with Ar have been measured at broadly tunable energies documenting the versatility of the instrument. Future applications in stereodynamics and cold state-to-state collisions of vibrationally excited polyatomic molecules are briefly discussed.

Visualizing rotational wave functions of electronically excited nitric oxide molecules by using an ion imaging technique.

Here we report the dissociative ionization imaging of electronically excited nitric oxide (NO) molecules to visualize rotational wave functions in the electronic excited state (A 2Σ+). The NO molecules were excited to a single rotational energy eigenstate in the first electronic excited state by a resonant nanosecond ultraviolet pulse. The molecules were then irradiated by a strong, circularly polarized femtosecond imaging pulse. Spatial distribution of the ejected N+ and O+ fragment ions from the dissociative NO2+ was recorded as a direct measure of the molecular axis distribution using a high-resolution slice ion imaging apparatus. The circularly polarized probe pulse realizes the isotropic ionization and thus undistorted shapes of the functions can be visualized. Due to the higher ionization efficiency of the excited molecules relative to the ground state ones, signals from the excited NO were enhanced. We can, therefore, extract shapes of the square of rotational wave functions in the electronic excited state although the unexcited ground state molecules are the majority in an ensemble. The observed images show s-function-like and p-function-like shapes depending on the excitation wavelengths. These shapes well reflect the rotational (angular momentum) character of the prepared states. The present approach directly leads to the evaluation method of the molecular axis alignment in photo-excited ensembles, and it could also lead to a visualization method for excited state molecular dynamics.

Relaxation mechanism and the detection of collision quenching rate of excited NO2 molecules

Laser induced fluorescence dispersive (LIFD) spectrum of NO2 is obtained at 2.66Pa sample pressure and with 532nm laser as radiation source. The spectrum is composed of four vibration series which comes from the transition of excited molecules distributed in different energy levels. It will develop into a continuous envelope centered at the position of 630.7nm when the pressure exceeds 66.5Pa. The center wavelength presents red shift with the increase of pressure. These results show that apart from radiation, the dominant depopulation way of excited molecules is collision. The excited energy is converted into translation one by collision and generates sound wave further. The photoacoustic (PA) spectrum of NO2 in 520–600nm wavelength region is collected. It consists of banded structure which is assigned to the first excited electronic state. The collision quenching rate is acquired by measuring the variation of PA signal versus sample pressure. The optimum excitation and detection wavelengths are decided for the detection of NO2.

Absorption Dynamics of Nitric Oxide in Gas Mixtures Excited by Pulsed Discharge

Vibrational relaxation of NO molecules excited by a pulsed e-beam sustained discharge (EBSD) with the use of CO laser probing was studied. We developed numerical model of vibrational kinetics in ensemble of NO molecules due to comparing the experimental and calculated data on absorption dynamics of vibrational excited NO molecules.

Direct measurement system of nitrogen dioxide in the atmosphere using a blue light-emitting diode induced fluorescence technique.

An instrument for measuring atmospheric nitrogen dioxide has been developed by a light-emitting diode induced fluorescence (LED-IF) technique. Air was introduced into a fluorescence detection cell. A pulsed blue light LED with a peak wavelength of 430 nm was irradiated to excite NO2 molecules in this cell. Fluorescence emitted from excited NO2 molecules was detected by a dynode-gated photomultiplier tube. The current detection limit of the LED-IF instrument was estimated to be 7.0 and 0.91 ppbv (parts per billion by volume) at 1-min and 1-h integration times, respectively, with a signal to noise ratio of 2. This result indicates that this LED-IF instrument can measure sufficiently precise 1-h values of NO2 concentrations in the urban atmosphere. An NO2 test observation and an intercomparison of the LED-IF instrument with an NO2 measurement system based on a photolytic converter/NO-O3 chemiluminescence method were performed in the urban atmosphere. Concentration differences between the two methods were within ±25% for about 90% of the data. It has been demonstrated by these observations that NO2 concentrations can be observed in the urban areas using the LED-IF instrument.

Dynamical steering in an electron transfer surface reaction: Oriented NO(v = 3, 0.08 < Ei < 0.89 eV) relaxation in collisions with a Au(111) surface

We report measurements of the incidence translational energy dependence of steric effects in collisions of NO(v = 3) molecules with a Au(111) surface using a recently developed technique to orient beams of vibrationally excited NO molecules at incidence energies of translation between 0.08 and 0.89 eV. Incidence orientation dependent vibrational state distributions of scattered molecules are detected by means of resonance enhanced multiphoton ionization spectroscopy. Molecules oriented with the N-end towards the surface exhibit a higher vibrational relaxation probability than those oriented with the O-end towards the surface. This strong orientation dependence arises from the orientation dependence of the underlying electron transfer reaction responsible for the vibrational relaxation. At reduced incidence translational energy, we observe a reduced steric effect. This reflects dynamical steering and re-orientation of the NO molecule upon its approach to the surface.

Extended hydrodynamic approach to quantum-classical nonequilibrium evolution. II. Application to nonpolar solvation

The mixed quantum-classical formulation derived in our companion paper [D. Bousquet, K. H. Hughes, D. Micha, and I. Burghardt, J. Chem. Phys. 134, 064116 (2011)], which is based upon a hydrodynamic representation of the classical sector, is applied to nonequilibrium nonpolar solvation dynamics as exemplified by the solvation of the electronically excited NO molecule in a rare gas environment. Derived from a partition of the Hamiltonian into a primary (quantum) part and a secondary (classical) part the hydrodynamic equations are formulated for multi-quantum states and result in explicit equations of motion for populations and coherences. The hierarchy of hydrodynamic equations is truncated by the following approximate closure schemes: Gauss-Hermite closure, dynamical density functional theory approximation, and a generalized Maxwellian closure. A comparison of the dynamics using these three closure methods showed that the suitability of a particular closure scheme was dependent on the initial conditions and the nonequilibrium character of the dynamics.

Electron Kinetic Energies from Vibrationally Promoted Surface Exoemission: Evidence for a Vibrational Autodetachment Mechanism

We report kinetic energy distributions of exoelectrons produced by collisions of highly vibrationally excited NO molecules with a low work function Cs dosed Au(111) surface. These measurements show that energy dissipation pathways involving nonadiabatic conversion of vibrational energy to electronic energy can result in electronic excitation of more than 3 eV, consistent with the available vibrational energy. We measured the dependence of the electron energy distributions on the translational and vibrational energy of the incident NO and find a clear positive correlation between final electron kinetic energy and initial vibrational excitation and a weak but observable inverse dependence of electron kinetic energy on initial translational energy. These observations are consistent with a vibrational autodetachment mechanism, where an electron is transferred to NO near its outer vibrational turning point and ejected near its inner vibrational turning point. Within the context of this model, we estimate the NO-to-surface distance for electron transfer.

Efficiency determination of the laser-induced reaction of NO(A( 2Σ +)) with CO 2

The reaction of NO excited in the electronic state A( 2Σ +, v′ = 2) with CO 2 has been studied. This has been carried on by irradiating NO samples in excess of CO 2 with a home-made dye laser pumped by a commercial frequency tripled Nd:YAG laser. The samples have been analyzed by FTIR spectrometry before and after irradiation to obtain the fraction of molecules reacted per pulse. The NO excitation efficiency was determined from the measurement of the absorption cross-section, the sample transmittance and the energy of the laser pulse. A value of (0.26 ± 0.01) was obtained for the reaction efficiency, indicating that about 25% of the excited NO molecules reacted with CO 2. A reaction rate constant value of (1.30 ± 0.12) × 10 −10 cm 3 molecules −1 s −1 was determined from the value of the reaction efficiency obtained in this work and the global electronic quenching rate constant of NO(A 2Σ +, v′ = 2) reported by Nee et al. [6] for CO 2.

Distribution of the ultraviolet nitric oxide Martian night airglow: Observations from Mars Express and comparisons with a one‐dimensional model

Limb observations with the SPICAM ultraviolet spectrometer on board the Mars Express orbiter revealed ultraviolet nightglow emission in the δ (190–240 nm) and γ (225–270 nm) bands of nitric oxide. This emission arises from radiative recombination between O(3P) and N(4S) atoms that are produced on the day side and form excited NO molecules on the night side. In this study, we analyze the night limb observations obtained during the MEX mission. In particular, we describe the variability of the emission brightness and its peak altitude. We examine possible correlations with latitude, local time, magnetic field strength or solar activity. We show that the altitude of maximum emission varies between 55 and 92 km while the brightness is in the range 0.2 to 10.5 kR. The total vertical emission rate ranges from 8 to 237 R with an average value of 36 ± 52 R. The observed topside scale height of the emission profile varies between 3.8 and 11.0 km, with a mean value of 6 ± 1.7 km. We use a chemical‐diffusive atmospheric model where the eddy coefficient, whose value in the Mars thermosphere is uncertain, is a free parameter to match the observed peak altitude of the emission. The model solves the continuity equation for O(3P), N(4S), and NO using a finite volume method on a one‐dimensional grid. We find that the downward flux of N atoms at 100 km varies by two orders of magnitude, ranging from 107 to 109 atoms cm−2 s−1.

Limb observations of the ultraviolet nitric oxide nightglow with SPICAV on board Venus Express

Limb observations of the spectrum of nightglow emission in the δ (190–240 nm) and γ (225–270 nm) bands of nitric oxide have been made with the Spectroscopy for Investigation of Characteristics of the Atmosphere of Venus (SPICAV) ultraviolet spectrometer on board Venus Express. These emissions arise from radiative recombination between O(3P) and N(4S) atoms that are produced on the dayside and recombine to form excited NO molecules on the nightside. No other emission feature has been identified. The mean altitude of the emission layer is located at 113 km, but it varies between 95 and 132 km. The mean brightness of the total NO emission at the limb is 32 kR, but it is highly variable with limb intensities as large as 440 kR observed at low latitude and values below 5 kR seen at northern midlatitudes. No systematic dependence of the brightness with latitude is observed, but the mean altitude of the emission maximum statistically drops with increasing latitude between 6° and 72°N. Typical observed limb profiles are compared with simulations based on a one‐dimensional chemical‐diffusive atmospheric model. From model fits to observed profiles, we find that the downward flux of N atoms at 130 km typically varies between 1 × 108 to 4 × 109 atoms cm−2 s−1. Comparisons of observed airglow topside scale heights with modeled profiles smoothed by the instrumental field of view indicate that the observations are compatible with a downward flow of O and N atoms by molecular and turbulent transport above the peak of emission. The K coefficient deduced from comparisons to limb profiles is less than that determined from the observations made with the Pioneer Venus UV spectrometer at low latitude during periods of high solar activity.

Parity-dependent rotational rainbows in D2–NO and He–NO differential collision cross sections

The (j', Omega', epsilon') dependent differential collision cross sections of D2 with fully state selected (j = 12, Omega = 12, epsilon = -1) NO have been determined at a collision energy of about 550 cm(-1). The collisionally excited NO molecules are detected by (1+1') resonance enhanced multiphoton ionization combined using velocity-mapped ion-imaging. The results are compared to He-NO scattering results and tend to be more forward scattered for the same final rotational state. Both for collisions of the atomic He and the molecular D2 with NO, scattering into pairs of rotational states with the same value of n = j' - epsilon epsilon'2 yields the same angular dependence of the cross section. This "parity propensity rule" remains present both for spin-orbit conserving and spin-orbit changing transitions. The maxima in the differential cross sections-that reflect rotational rainbows-have been extracted from the D2-NO and the He-NO differential cross sections. These maxima are found to be distinct for odd and even parity pair number n. Rainbow positions of parity changing transitions (n is odd) occur at larger scattering angles than those of parity conserving transitions (n is even). Parity conserving transitions exhibit-from a classical point of view-a larger effective eccentricity of the shell. No rainbow doubling due to collisions onto either the N-end or the O-end was observed. From a classical point of view the presence of a double rainbow is expected. Rotational excitation of the D2 molecules has not been observed.