Rate Parameters for Electronic Excitation of Diatomic Molecules: NO Radiation

Abstract

This is one of an ongoing series of papers on collisional excitation of electronic states in N 2 , O 2 , NO, CO, CN, and N 2 . In this paper, NO radiation observed in the test section of an arcjet wind tunnel is studied. In the experiments, NO and were seen, was not seen, and " was seen to be very weak. NO radiation is calculated with the use of the code SPRADIAN07 to explain the measured spectra. It was found that inverse predissociation is mainly responsible for the population of the NO C 2 r state during recombination of N and O atoms. The population of the NO A 2 state is mostly due to the radiative decay from the NO C 2 r state. The NO D 2 state is excited from the C 2 r state by collisions. The NO B 2 r state is populated by complicated collisional transition paths by passing through the intermediate states a 4 r and b 4 . These interpretations at least qualitatively explain the experimental data. Electronic excitation temperature is only remotely related to electron temperature. Nomenclature A = electronic state of the NO molecule, A 2 A h = excitation rate parameter, cm 3 =s A r = radiative transition probability, s 1 a = electronic state of the NO molecule, a 4 B = electronic state of the NO molecule, B 2 r b = electronic state of the NO molecule, b 4 C = electronic state of the NO molecule, C 2 r D = electronic state of the NO molecule, D 2 E = electronic term energy, cm 1 ; energy, cm 1 g = statistical weight (multiplicity, degeneracy) h = Plank constant, 6:6261 10 34 J s I = total band intensity, W=cm 3 I = specific intensity, W=cm 2 m sr i = electronic state i of the NO molecule J = rotational quantum number; rotational state j = electronic state j of the NO molecule K e = excitation rate by electron collision, cm 3 =s K h= excitation rate by heavy-particle collision, cm 3 =s K ivpr = rate coefficient for inverse predissociation, cm 3 =s K prd = rate coefficient for predissociation, s 1 k B = Boltzmann constant, 1:3807 10 23 J=K k = absorption coefficient, cm 1 M = colliding heavy particle or electron m = mass, g=mol n = number density, cm 3 ; excitation rate parameter, Eq. (10) p = pressure, atm Q = partition function S = spin angular momentum quantum number S J 0 0 J 00 00 = rotational line strength factor (Hönl-London factor) s = distance along a ray, cm T = heavy-particle translational temperature, K T d = activation temperature, K T e = electron temperature, K T ex = electronic excitation temperature, K T r = heavy-particle rotational temperature, K T v = vibrational temperature, K t = time, s v = vibrational quantum number, vibrational state X = ground electronic state of the NO molecule, X 2 r x = distance from the nozzle exit = NO B 2 r X 2 r transition = NO A 2 X 2 r transition = NO C 2 r X 2 r transition K = Kronecker delta " = NO D 2 X 2 r transition " = emission coefficient, W=cm 2 m sr = nonequilibrium factor = wavelength, Å or nm = orbital angular momentum quantum number about the internuclear axis = frequency, Hz = cross section, cm 2 = total mole fraction Subscripts A = electronic sta...

Spectroscopic determination of vibrational and rotational temperatures of NO molecules in N2–O2mixture microwave discharge

“…We also considered the effect of spectral contamination of ¢-band (B 2 ¬ ¼ X 2 ¬) 23) and ¤-band (C 2 ¬ ¼ X 2 ¬) 20) on £-band radiation of NO. We know that the ¤-band has a comparable intensity with £-band 26) under low-temperature and low-density discharge plasma, but its strong peaks at shorter wavelength area than 200 nm.…”

Reaction of the N Atom with Electronically Excited O2 Revisited: A Theoretical Study

“…Indeed, as seen in Figure , the corresponding 6 TS 0 structure lies ≈3.5 eV above the reactants. Nevertheless, since the reverse reaction has no substantial energy barrier (there is a fairly deep intermediate complex 6 IM 0 on the product side of the 6 TS 0 transition state), the reaction channel backward to (c) may be of interest for kinetics of electronically excited NO states, which is important for describing the nonequilibrium radiation from heated air …”

“…Nevertheless, since the reverse reaction has no substantial energy barrier (there is a fairly deep intermediate complex 6 IM 0 on the product side of the 6 TS 0 transition state), the reaction channel backward to (c) may be of interest for kinetics of electronically excited NO states, which is important for describing the nonequilibrium radiation from heated air. 155 As for the N + O 2 (a 1 Δ g ) reacting system, by virtue of the twofold orbital degeneracy of molecular oxygen in the singlet delta state, 76,156 the interaction of N with O 2 (a 1 Δ g ) can occur along two different PESs, resulting in the formation of the ground-state NO(X 2 Π) + O( 3 P) bimolecular products via the transition states 4 TS 1 [pathway (d)] and 4 TS 2 [pathway (e)] of different energies. The obtained values of energy barriers for pathways (d) and (e) are 0.619 and 1.964 eV, respectively.…”

Expansion of the equilibrium constants for the temperature range of 300K to 20,000K

“…Such an electronic grouping model was validated in the nonBoltzmann radiation calculations of CN [12] and NO [13], and this grouping model is useful in reducing the computational resources without losing the characteristics of the electronic Table 1. Electronic states and energies of C and N atoms [1], and N 2 + radiates strongly in the shock layer.…”

“…The recombination rates calculated by the present equilibrium constants is larger than those of the previous values, and the species mole-fraction of O by the present equilibrium constants is twice less than that by the previous equilibrium constants. (13) respectively. γ is the specific heat ratio and p t , ρ t , T t are the pressure, density, and temperature at the stagnation conditions.…”