Intensity of the sulfur dioxide rotational spectrum

The integral band intensity of the pure rotational absorption of SO₂ gas has been determined from far-i.r. spectra. From the curve of growth, the value at 298°K is found to be S^o_b = 35.2±1.5atm^-1 -cm^-2. The entire set of experimental data has been analyzed using an absorption band model. The derived intensity agrees with that obtained from the curve of growth to be better than 10%. This result should be of value in connection with atmospheric models of the planet Venus.     

Absorption by self-broadened rotational lines in the v4-fundamental of 12CH4

Spectral transmission measurements at 300°K in the v₄-fundamental of ¹²CH₄ are presented for pure samples of the gas. A line-by-line computation using S⁰_v = 145 cm^-2 atm^-1 at STP, measured by us earlier, is in good agreement with the present data on self-broadened lines.     

Invariant combinations of coefficients in the rotational Hamiltonian

A general development of combinations of parameters in the asymmetric rotor Hamiltonian, which are independent of the coefficients of the contact transformation operators used in the reduction of that Hamiltonian, is given. These invariant combinations are obtained for a Hamiltonian containing up to eighth degree operators. The adaptation to the A and S forms of the Watson Hamiltonian and their utility in conversion of coefficients from one form to another is discussed.     

The pure rotational atmospheric lines of hydroxyl

Pure rotational line positions of the hydroxyl radical (OH) have been calculated for all vibrational levels expected in the earth's atmosphere (v = 0–9) and for lower rotational quantum numbers J″=0.5–12.5. These positions have been tabulated and compared with those derived from energy levels obtained from precise near-i.r. vibration-rotation bands and show good agreement for low J″ values. A tentative identification has been made of three v = 0 lambda-type doublets in a high-resolution far-i.r. (30–120 cm^-1) emission spectrum of the atmosphere obtained at 30 km from a balloon-borne platform. Line strength (S_J′J″) and integrated intensity (S_q cm^-2atm^-1) values have been derived for these pure rotational transitions as an aid to further work and instrument design.     

Intensity measurements,self-broadening coefficients,and rotational intensity distribution for lines of the oxygen B band at 6880 Å

Quantitative measurements of intensities and half-widths were made for individual rotational lines of the atmospheric oxygen B band. The total band intensity, as derived from the line intensity measurements, is 40·8±0·6 cm^?1km^?1atm^?1 STP. As had been previously found in this laboratory for the oxygen A band, the relative line intensities conform closely to the rotational distribution calculated by either Schlapp or by Watson. The line half-widths at half-intensity were determined for oxygen self-broadening for the ${}^{\mathrm{P}}\text{Q}$ and ${}^{\mathrm{P}}\text{P}$ branch lines and for a few ${}^{\mathrm{R}}\text{Q}$ and ${}^{\mathrm{R}}\text{R}$ branch lines near the band origin, and were found to vary from 0·064 cm^?1atm^?1 at J′ = 1 to 0·042 cm^?1atm^?1 at J′ = 25.     

The microwave spectrum and rotational structure of the Δ and Σ electronic states of sulfur monoxide

The spectrum of ¹Δ and ³Σ SO has been studied in the millimeter and submillimeter region of the microwave spectrum. This expanded spectral coverage has made possible the measurement of twenty-two previously unobserved transitions, several of which are necessary for an accurate calculation of the energy levels. As a result, it is now possible to calculate the rotational transitions between energy levels for which J ≤ 10 in both the ground ³Σ electronic state and the excited ¹Δ electronic state to an accuracy comparable to that of the microwave measurements themselves ( 1 MHz). Among the molecular constants calculated are; for the ¹Δ state: B₀ = 21 295.405 MHz, D₀ = 0.0350 MHz, ω_e = 1108 cm⁻¹, and r₀ = 1.4920 Å; and for the ³Σ state: B₀ = 21 523.561 MHz, D₀ = 0.03399 MHz, λ₀ = 158 254.387 MHz, γ₀ = −168.342 MHz, ₀ = 0.305 MHz, r₀ = 1.4840 Å, B_e = 21 609.552 MHz, λ_e = 157 779.2 MHz, and r_e = 1.4811 Å.     

Radiation emission coefficients for sulfur hexafluoride arc plasmas

Calculations are made of the total spectral absorptivities of plasmas of sulfur hexafluoride for wavelengths of 100 to 15,500 Å. Both line and continuum radiation are considered. For the contributions from line radiation, we have calculated the strengths, widths and shifts of both neutral, singly and doubly ionized atoms of S and F, except that we used experimental line strengths where they are available. The theory used was that of Griem, which assumes LS coupling. Curves are given for the emission coefficient of radiation appropriate to the arc center for isothermal cylindrical plasmas of various radii for pressures of 1 and 10 atm and temperatures from 5000 to 35,000°K. It is found that at 1 atm line radiation can be an order of magnitude higher than continuum radiation and radiation >2000 Å is less than 10% of the total radiation for temperatures greater than 15,000°K. Predictions are given of volt-ampere characteristics and central temperatures for arcs of various radii in SF₆ at pressures at 1 and 10 atm.     

Line-shape parameters in infrared bands of sulfur dioxide

This paper presents the calculated results for line-shape parameters in the v₁ and v₃ bands of sulfur dioxide for temperatures between 300 and 1200°K, together with the self-broadening coefficients for some particular rotational lines. The Anderson-Tsao-Curnutte theory was applied to calculate the line half-widths, and a criterion was introduced to determine the line-shape parameters on the basis of a narrow-band model. The calculated results are greatly different from previously assumed values.     

Single vibronic level fluorescence spectra of sulfur dioxide

Single vibronic level fluorescence spectra of sulfur dioxide have been recorded throughout most of the region corresponding to the $\text{A}\text{?}\text{-}\text{X}\text{?}$ absorption. These spectra show progressions in the symmetric stretching mode of at least five members. Twelve origins between 30 972 and 31 776 cm^?1 show remarkably similar Franck-Condon (FC) patterns for this progression. Seven origins between 31 840 and 32 257 cm^?1 show another distinct FC pattern. This behavior is repeated for three more regions of excitation, each with a different distinct FC pattern and each containing numerous origins spread throughout a region of about 700 cm^?1. The progressions in the symmetric bending mode are essentially absent in the lowest energy excitation spectra and then slowly increase in length as the excitation energy increases. There is limited activity in both even and odd quanta of the antisymmetric stretching mode. These results are interpreted in terms of the levels of a zero-order ¹B₁ electronic state (with zero-order origin at around 31 240 cm^?1) that are very strongly vibronically coupled to many more ¹A₂ levels (with lower energy zero-order origin). The bulk of the emission is what would be expected from the zero-order ¹B₁ levels spread among the ¹A₂ levels.     

Collisional broadening and shifting of OCS rotational spectrum lines

Broadening and shifting of carbonyl sulfide (OCS) rotational spectrum lines by pressure of N₂, O₂ and OCS were accurately studied in the frequency range 24–850 GHz at room temperature using a spectrometer with radio-acoustic detection of absorption. Rotational dependences of collisional widths of OCS spectrum lines were determined by a simple empirical polynomial fit of experimental data. Experimental uncertainties were analyzed. Results of supplementary test measurements of self-broadening of rotational OCS lines in the ν₂ excited vibrational state and carbon monoxide (CO) lines in the ground vibrational state are presented. Comparison of the obtained results with previously known measurements and theoretical calculations is given. The performed work allows for the first time development of accurate gaseous etalon of absorption for atmospheric applications and laboratory use, covering continuously the whole millimeter- and submillimeter-wave range.     

Computed values of rotational collision number and diffusion coefficients for oxygen

Recent experimental data on thermal conductivity and viscosity are used to calculate values of rotational collision numbers and diffusion coefficients for oxygen in the temperature range 400–1600 K.     

Experimental studies of the radiative properties of sulfur dioxide

The narrow band-model parameters S/d, γ_N/d and B have been obtained experimentally for the infrared bands of SO₂. Good agreement was obtained between the present experimental and previous theoretical studies. The revised wide band-model parameters were determined and used to calculate total gas emissivities, which are found to be considerably different from previously published values.