The lowest s Rydberg complex of CIF: c3Πi and C1Π

The absorption spectrum of CIF in the region 1400-1290 Å has been photographed at a dispersion of 0.18 Å/mm. The spectrum consists of bands degraded to shorter wavelengths and arises from transitions to the four components c³Π₂, c³Π₁, c³Π₀, and C¹Π₁ of the first s Rydberg complex built on the X²Π_i core of CIF⁺. Strong spin-orbit interactions distort the spin splitting of the triplet state and produce an unusual intensity distribution in the weak c³Π₀ ← X¹Σ⁺ transition. Upper state vibrational and rotational constants are given for the more abundant isotope ³⁵CIF.     

Line strengths and self-broadened linewidths of N2O in the 2-μm region: 2400-0000 and 0112-0000 transitions

The strenghths and self-broadened linewidths of the parallel 24⁰0-00⁰0 and perpendicular 01¹2-00⁰0 bands of N₂O have been measured with a precision better than 3%, using a deconvolution procedure. For both transitions, the coefficient of the vibration-rotation interaction polynomial, the values of the rotationless dipolar transition moment, and the band intensity have been calculated from the line strengths. For the total intensity the values found are S_00⁰0²⁴⁰⁰ = (1.325 ± 0.021) × 10^?2 cm^?2·atm^?1 and S_00⁰0⁰¹¹² = (1.209 ± 0.018) × 10^?2 cm^?2·atm^?1.     

Deperturbation study of the 0–1 band of the d3Πi-b3Πr transition of the SiO molecule

The structure of the (0–1) band of the d³Π_i-b³Π_r system of SiO has been photographed under high resolution with a chemiluminescent flame source, and a rotational analysis has been carried out. All theoretically predicted 27 branches of the d³Π_i-b³Π_r transition have been identified. The upper-state level is shown to be perturbed by the v = 23 level of the A¹Π state. Due to mixing of the A¹Π with the d³Π, the (23-1) band of the A¹Π-b³Π_r transition has also been observed. The deperturbed molecular constants of the d³Π_i and A¹Π levels have been evaluated.     

Measurement at different temperatures of absolute intensities,line half-widths,and broadening by Ar and N2 for the 3001II←0000 band of CO2

Absolute intensities, self-broadening coefficients, and foreign-gas broadening by Ar and N₂ were measured at temperatures of 197, 233 and 294 K for the 30⁰1_II←00⁰0 band of CO₂ at 6348 cm^-1. Also, the intensity parameters and total band intensity were calculated. We obtained for the vibration-rotation interaction factor the value F(m) = 1 + (0.26 ± 0.06) × 10^-2m + (0.92 ±0.32 × 10^-4 m²; for the purely vibrational transition moment, we found ¦R₀₀₀₀^3001_II¦к(0.4351 ± 0.0014)()10^b3 debye; and, for the total band intensity at STP conditions, S_band(30⁰1_II←00⁰0)_STP = 1255 ± 9 cm^-1 km^-1 atm^-1.Self-broadening coefficients at 197 and 294 K were also measured, as well as broadening by Ar and N₂. Foreign-gas-broadening efficiencies (Ar and N₂) were determined. Finally, a comparison is made with measurements by other authors and with theoretically calculated values.     

Ab initio calculation of transition dipole moments for transitions between valence states in oxygen molecules

Results of ab initio calculations of potential-energy curves for 20 singlet and 20 triplet valence states of oxygen with configuration interaction taken into account in the 6-31G basis are presented. Transition dipole moments of triplet-triplet (1³Π_g ← B ³Σ _u ^? , 1³Π_g ← A ³Σ _u ⁺ , 1³Π_g ← A′ ³Δ_u, B ³Σ _u ^? ← X ³Σ _g ^? , 2³Π_u ← 1³Π _g, 2³Σ _g ^? ← B ³Σ _u ^? , 1³Π_u ← X ³Σ _g ^? , 2³Π_u ← X ³Σ _g ^? , 2³Π _g ← A′³Δ_u, 3³Π_g ← A′ ³Δ _u, 2³Δ_u ← 2³Π_g, 3³Π_g ← B ³Σ _u ^? , and 2³Π_g ← A ³Σ _u ⁺ ) and singlet-singlet (2¹Σ _g ⁺ ← 2¹Π_u, 2¹Π_u ← 1¹Π ^g, ¹Π_u ← 2¹Δ_g, 1¹Π_g ← c ¹Σ _u ^? , ¹Π_u ← b ¹Σ _g ⁺ , 1¹Δ _u ← a ¹Δ_g, 2¹Π_u ← a ¹Δ_g, 2¹Δ_g ← 1¹Δ_u, ¹Π _u ← a ¹Δ _g, 1¹Π_u ← b ¹Σ _g ⁺ , 2¹Π_g ← 1¹Π_u, 2¹Π _g ← c ¹Σ _u ^? , 1¹Δ _u ← 1¹Π _g, f′Σ _u ⁺ ← b ¹Σ _g ⁺ , 2¹Σ _g ⁺ ← f ′¹Σ _u ⁺ , 3¹Π_g ← 1¹Δ_u) radiative transitions are calculated as functions of internuclear separation. The possibility of observing these transitions under experimental conditions is discussed.     

Shock-tube study of HCN self-broadening and broadening by argon for the P(10) line of the ν1 band at 3 μm

A tunable infrared diode laser was used to measure the fully resolved absorption line shape of the P(10) line in the ν₁ band (10°0–00°0) of HCN for shock-heated mixtures of HCN-Ar at temperatures of 1000, 1500 and 2000 K. The temperature dependence of the collision-broadening coefficients 2γ (cm^-1 atm^-1, FWHM) were inferred for both self-broadening and broadening by argon. For the assumed form 2γ = 2γ₀(T₀/T)ⁿ the exponent n was determined to be 0.63 ± 0.06 with 2γ₀ = 0.11 cm^-1atm^-1 and T₀ = 300 K for argon-broadening in the range 300 < T < 2000 K, and 1.2 ± 0.6 with 2γ₀ = 0.68 cm^-1atm^-1 and T₀ = 1000 K for self-broadening in the range 1000 < T < 2000 K.     

Theoretical integrated intensities for the 2ν2 and 2ν2-ν2 bands of HCN and DCN

Dipole moment functions, both perpendicular and parallel to the molecular axis, are calculated from the SCF and MRD-CI results of a previous study for the normal ν₂ bending vibrations of HCN and DCN. Vibrationally averaged dipole moments and the infrared transition matrix elements are then obtained from the dipole moment functions and vibrational wave functions. MRD-CI results, with known experimental values in parentheses, for HCN are 〈0|μ|0〉 = ?2.954(?2.985) D, 〈1|μ|1〉 = ?2.915(±2.942) D, 〈0|μ|1〉 = 0.148(0.147) D, 〈0|μ|2〉 = ?0.027 D, 〈1|μ|2〉 = 0.210 D. Calculated absolute intensities at 1 atm and 0°C for the (02⁰0) ← (000), (02⁰0) ← (010), and (02²0) ← (010) bands of HCN are 25 (40 ± 10 as estimated from spectra), 8.5, and 17.0 atm^?1 cm^?2, respectively. Results for DCN are also reported.     

Intensity measurements in freon bands of atmospheric interest

The absolute intensities of the i.r. absorption bands, which are located in the atmospheric window region, of CFCl₃ (“Freon-11”) and CF₂Cl₂ (“Freon-12”) have been measured at 300°K. Our best estimates for these parameters are: for CFCl₃ (“Freon-11”), S_v = 635±36 cm^-2atm^-1 (9.2μ band), S_v = 1536±45 cm^-2atm^-1 (11.8μ band); for CF₂Cl₂ (“Freon-12”), S_v = 718±14 cm^-2atm^-1 (8.7μ band), S_v = 1136±22 cm^-2atm^-1 (9.1μ band), and S_v = 1302±40 cm^-2atm^-1 (10.9μ band).     

Doppler-limited dye laser excitation spectroscopy of HCF

The cw dye laser excitation spectrum of the $\text{A}\text{?}{}^1\text{A″(000) ←}\text{X}\text{?}{}^1\text{A′(000)}$ vibronic band of HCF was observed between 17 188 and 17 391 cm^?1 with the Doppler-limited resolution, 0.04 cm^?1. The HCF molecule was produced by the reaction of discharged CF₄ with CH₃F, and 853 lines were observed, of which 516 transitions were assigned to K′_a ← K″_a = 3 ← 4, 2 ← 3, 1 ← 2, 0 ← 1, 1 ← 0, 2 ← 1, 0 ← 0, 1 ← 1, 2 ← 2, 3 ← 3, 2 ← 0, and 0 ← 2 subbands. A rotational analysis yielded the rotational constants and quartic and sextic centrifugal distortion constants for both the $\text{A}\text{?}$ and $\text{X}\text{?}$ states and the band origin, with good precision. The molecular constants determined reproduce the observed transition frequencies with an average deviation of 0.0038 cm^?1. Small rotational perturbations in the excited state were found at J = 5, 6 and J = 10, 11 of J_1,J and at J = 15, 16 of J_2,J?1 levels.     

R-branch head of the ν3 band of CO2 at elevated temperatures

The R-branch head of the 00⁰1 ← 00⁰0 band of ¹²C¹⁶O₂ has been recorded with Doppler-limited resolution using a tunable laser difference-frequency spectrometer. J values to 140 were measured at temperatures to 985 K. The data have been combined with extremely precise transition frequencies for 0 ≤ J ≤ 76 measured with a Fourier transform interferometer to obtain an improved set of spectral constants for this ν₃ band of CO₂.     

Magnetic rotation observation of the C2b3Σg− ← a3Πu transition using a color center laser

The magnetic rotation observation of the C₂b³Σ_g^? ← a³Π_u Ballik-Ramsay system using a color center laser is reported. This is the first detection of this system in absorption. Three bands, 0 ← 1, 1 ← 2, and 2 ← 3, were identified in the spectral range 3650–4030 cm^?1. The last two bands were observed for the first time. In magnetic rotation many satellite lines (ΔN ≠ ΔJ) which would be very weak in normal absorption have been observed with intensity comparable to the main branch lines. This permits a slight improvement in the accuracy of some of the fine structure constants. A variety of lineshapes are observed for the various branches by magnetic rotation. Because the b³Σ_g^? fine structure is small, giving a partial overlap, the peak frequency of a magnetic rotation signal usually does not correspond to the center frequency of the normal absorption signal of that transition. A computer program has been written to predict magnetic rotation lineshapes and obtain the peak frequency displacements. Various observed and calculated lineshapes are displayed and compared.     

High resolution infrared spectrum of 13CS2 between 250 and 430 cm−1

The high resolution infrared spectrum of ¹³CS₂ between 250 and 430 cm^?1 has been studied with a Fourier transform spectrometer at a resolution of about 0.010 cm^?1. The following bands are analyzed: the bending fundamental 01¹0←00⁰0 of ¹³C³²S₂ and the associated “hot” bands 02²0←01¹0, 02⁰0←01¹0, 03³0←02²0, 03¹0←02⁰0, 03¹0←02²0, 11¹0←10⁰0, the difference band 10⁰0←01¹0 of ¹³C³²S₂, and the bending fundamental 01¹0←00⁰0 of ³²S¹³C³⁴S. The polynomial fits were used in the analyses. The rotational constants B and D together with the vibrational term values have been derived for the states involved. The l-type doubling constant q has been obtained for the Π-states 01¹0, 11¹0, and 03¹0 of ¹³C³²S₂.     

Absorption measurements of H2O at high temperatures using a CO laser

Absorption of CO laser radiation (v = 8→7, J = 14→15 transition at 1901.762 cm^-1) by H₂O has been studied in shock-heated H₂/O₂/Ar mixtures over the temperature range 1300–2300 K. This laser transition is nearly coincident with the v₂-band 12_3,10←11_2,9 transition of H₂O at 1901.760 cm^-1, thereby providing a convenient and sensitive absorption-based H₂O diagnostic useful for studies of combustion. The collision-broadening parameter for this H₂O line, due to broadening by Ar, was determined to be 2γ (cm^-1atm^-1) = 0.027 (T/1300)^-0.9 in the temperature range 1300–2300 K. Calculations of the H₂O absorption coefficient (at 1901.762 cm^-1) based on this expression for 2γ are presented for the temperature range 300–2500 K and pressure range 0.3–1 atm.     

Accurate wavenumbers of the AΣ → XΠ (0, 0) and (1, 0) bands of OH and OD

The important A²Σ → X²Π (0, 0) absorption band of OH has been remeasured from spectra obtained by flash photolysis of H₂O₂ vapor. Accurate wavenumber measurements using thorium standards show that the previous rotational line measurements are about 0.1 cm^-1 too large. Measurements are also given for the (1, 0) band of OH and the (0, 0) and (1, 0) bands of OD.     

Tunable diode laser spectroscopy of CO2 in the 10- to 15-μm spectral region—Lineshape and Q-branch head absorption profile

The self-broadened and nitrogen-broadened absorption profiles of the Q-branch head of the 10⁰0 ← 01¹0 band of CO₂ near 618 cm^?1 were studied under high resolution (～10^?4 cm^?1) using tunable diode laser techniques. The intensity and linewidth of several lines in this Q branch, the ν₂ band, 10.4-μm and 9.4-μm laser bands have been measured accurately. The lineshape of a CO₂ line has also been measured to be Lorentzian within experimental accuracy to about 15 half-widths. Preliminary calculated Q-branch head absorption profiles agree reasonably well with the observed profiles.     

Absolute Line Intensities in Acetylene: The 1.5-μm Region

We measured 305 absolute line intensities in the ν₁+ν₃(Σ⁺_u)-0(Σ⁺_g) band of ¹²C₂H₂ and ¹³C¹²CH₂ and the ν₁+ν₂+(ν¹₄+ν⁻¹₅)⁰(Σ⁺_u)-0(Σ⁺_g), ν₁+ν₃+ν¹₄(Π_g)-ν¹₄(Π_g), and ν₁+ν₃+ν₅¹(Π_u)-ν₅¹(Π_u) bands of the main isotopomer, all observed near 1.5 μm. The absolute intensity of these bands are respectively 6.4882 (34), 0.12337 (10), 0.083746 (71), 0.58771 (28), and 0.32126 (11) cm⁻² atm⁻¹ at 296 K. In addition, we also determined Herman-Wallis factors for the first time in this spectral region.     

Strengths and air-broadened widths of H2O lines in the 2950–3400 cm-1 region

Measurements of the strengths and air-broadened widths of 223 lines of water vapor have been made with high resolution in the region 2950–3400 cm^-1. The strength data of the lines in the 2ν₂ and ν₁ bands are analyzed to determine the band strengths and the coefficients of the F factors. The band strengths of the 2ν₂ and ν₁ bands were found to be 1.75±0.08 and 10.3±1.1 cm^-2 atm^-1 at 296 K, respectively. The selection rules of the lines observed in the ν₃ band are forbidden in the symmetric-rotor limit. The majority of the measured strengths of these lines differ from the calculated values because of different asymmetries in the upper and lower vibrational states. Also, Coriolis perturbations in several lines of the ν₁ and ν₃ bands were observed in the strength measurements. The direct method was applied to determine the air-broadened line widths. The results are compared to the computed values of Benedict and Kaplan. There is good agreement between this work and the computed results for line width values greater than 0.05 cm^-1 atm^-1. However, for line widths less than 0.05 cm^-1 atm^-1, the measured values are smaller than the computed widths. A value of 0.018 cm^-1 atm^-1 is given for the width of the line at 3378.071 cm^-1, whereas the calculated value is 0.032 cm^-1 atm.     

Infrared diode laser spectroscopy of the BrO radical

The fundamental vibration-rotation band of the ⁷⁹BrO and ⁸¹BrO radicals in the ${}^2\text{Π}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ ground electronic state was observed in the region 700–760 cm^?1 by using a Zeeman-modulated infrared diode laser spectrometer. The BrO radical was generated directly in a multiple reflection Zeeman cell by a 60-Hz discharge in a mixture of Br₂ and O₂. The observed absorption lines, 20 and 22 in number for ⁷⁹BrO and ⁸¹BrO, rspectively, were combined with the microwave data of Cohen et al. [J. Mol. Spectrosc.87, 459–470 (1981)] and were subjected to least-squares analysis to determine the rotational and centrifugal distortion constants for both the v = 0 and v = 1 states and also the band origin. The band origin obtained for ⁸¹BrO, 721.92814(57) cm^?1, gives a support to the value 714 (10) cm^?1 estimated by Cohen et al. using the microwave data and also the result 722.1 ± 1.1 cm^?1 obtained by Barnett et al. [Canad. J. Phys.59, 1908–1916 (1981)] from a reanalysis of the A²Π_i-X²Π_i absorption spectrum.     

High-resolution optogalvanic study of the c4(0)1Πu, c′5(0)1Σu+, and a″(0)1Σg+ Rydberg states of N2

A new optogalvanic technique with an rf discharge was applied to a high-resolution study of the Rydberg states of N₂. The Ledbetter band, c₄(0)¹Π_u ← a″(0)¹Σ_g⁺, and a new visible band, c′₅(0)¹Σ_u⁺ ← a″(0)¹Σ_g⁺, were studied at a Doppler-limited resolution of 0.05 cm^?1. A Doppler-free method was also applied to resolve overlapped lines. Precise wavenumbers were determined for the rotational transitions of the two Rydberg bands. The rotational and the centrifugal constants for the lowest Rydberg state, a″(0)¹Σ_g⁺, were determined to be B₀ = 1.913748(42) cm^?1 and D₀ = 6.088(99) × 10^?6 cm^?1, where the numbers in parentheses are the standard deviation and apply to the last digits.     

A photoelectron spectroscopic study of the second ionisation of the CF(X2Π) radical

The CF(X²Π) radical has been re-investigated with vacuum ultraviolet photoelectron spectroscopy. Two bands were observed and assigned to the ionisations CF⁺(X¹Σ⁺)←CF(X²Π) and CF⁺(a³Π)← CF(X²Π). The first band, which has been observed previously, has an adiabatic ionisation energy of (9.11±0.02) eV and a vertical ionisation energy of (9.55±0.02) eV. For the second band, three vibrational components were observed with the first, the most intense, at an ionisation energy of (13.94±0.02) eV. Analysis of the vibrational structure in the two observed bands allowed ω_e and r_e to be determined as 1810±30 cm⁻¹ and 1.154±0.005 Å, respectively for the first ionic state, CF⁺(X¹Σ⁺), and 1614±30 cm⁻¹ and 1.213±0.005 Å, respectively for the second ionic state, CF⁺(a³Π). Comparison of the ionisation energies and spectroscopic constants obtained has been made with values obtained from recent multi-reference configuration interaction calculations.