The ν6 parallel band of cyclopropane at 3100 cm−1

The ν₆ fundamental of cyclopropane has been recorded on a 4.5-m vacuum spectrometer. Deconvolution of the spectrum has revealed considerably more detail than found in previous investigations. New information of a qualitative nature has been learned about the highly perturbed upper state and improved values of the band center and the upper-state rotational constant have been obtained. A lower-state combination-difference analysis using J values up to J = 23 has resulted in values of B″ and D″_J which are in excellent agreement with recent investigations. The following values of molecular constants, in wavenumber units (cm^?1), have been determined: B″ = 0.67023, D″_J = 0.93 × 10^?6, ν₀ = 3101.529, and B′ ? B″ = ?0.0019. The present data have been used with data from recent Raman and infrared spectra of C₃H₆ in a combined least-squares fit to the ground-state constants.     

The ν5 and ν3 Raman bands of CH2D2

The ν₅ and ν₃ Raman bands of CH₂D₂ have been recorded with a resolution of 0.35 cm^?1. The ν₃ state is well known from infrared studies. Three hundred twenty-nine transitions of the ν₅ band were analyzed, assuming an unperturbed upper state, giving a standard deviation on the fit of the upper-state energies of 0.037 cm^?1, The constants A, B, C, Δ_J, Δ_JK, and Δ_K differed significantly from the ground-state values, and ν₅ was determined as 1331.41 ± 0.05 cm^?1. This work represents the first complete analysis of the fine structure of a rotation-vibrational Raman band for an asymmetric rotor. The ν₅ state could not be analyzed in infrared so this investigation, once more, demonstrates the usefulness of the Raman method.     

Vibration-rotation spectra of ethane and deuteroethanes: The ν2 band of CH3CD3

The ν₂ band of CH₃CD₃ has been measured under an effective resolution of 0.04 cm^?1. About 400 transitions observed in the region from 2130 to 2060 cm^?1 have been identified as due to the ν₂ fundamental band. The least-squares analysis of these transitions yields the band constants: ν₀ = 2089.957, B′ = 0.548937, D_J′ = 6.97 × 10^?7, D_JK′ = 1.92 × 10^?6, A′ - A″ = ?0.01158, and D_K′ - D_K″ = 1.30 × 10^?6 cm^?1. The ground-state constants B″, D_J″, and D_JK″ are fixed to the values obtained from microwave spectroscopy.     

Laser Stark spectroscopy of the coriolis coupled ν2 and ν5 bands of CD3Cl

About 940 Stark resonances for CD₃³⁵Cl and 610 resonances for CD₃³⁷Cl have been measured by using a CO₂ laser with the 9- and 10-μm regions. They were assigned to 59 rovibrational transitions of ν₂ (J′ ≤ 37, K ≤ 14) and 200 of ν₅ (J′ ≤ 47, ?14 ≤ k′l′ ≤ +10) for ³⁵Cl, and 31 of ν₂ (J′ ≤ 12, K ≤ 10) and 175 of ν₅ (J′ ≤ 46, ?14 ≤ k′l′ ≤ +9) for ³⁷Cl. These data, combined with the microwave and FIR data in the ν₂ and ν₅ states, were analyzed by taking account of the Coriolis interaction between ν₂ and ν₅, and the (2, 2) and (2, ?1) interactions in ν₅. Several ΔK = +2 transitions of the ν₅ band were observed in the Stark spectra, and the ground state constants, A₀ and D_K0, were determined precisely for both ³⁵Cl and ³⁷Cl species. Also, the vibrationally induced dipole moments were obtained. The molecular constants and the zero-field transition frequencies of the ν₂ and ν₅ bands were determined.     

Acetylene spectra with a tunable diode laser: (ν4 + ν5)0+−ν41fQ branches of 12C2H2 and 12C13CH2

The rotational structure of the Q branches of the (ν₄ + ν₅)⁰⁺?ν₄^1f bands of ¹²C₂H₂ and ¹²C¹³CH₂ at 13.7 μm has been observed in a natural sample of acetylene by using a tunable diode laser as a source in a high-resolution infrared grating spectrometer equipped with a precision grating drive. Altogether 23 lines from J = 6 to 28 for ¹²C₂H₂ and 15 lines from J = 6 to 20 for ¹²C¹³CH₂ have been identified. The observed full width at half maximum of the resolved lines of these Q branches is very close to the calculated Doppler width. Molecular constants ν₀ + B″, B′ ? B″ ? 2D″, D′ ? D″, and H′ ? H″ have been derived from the measured line positions of the rotational structure.     

Diborane: High resolution infrared rovibration studies of 11B2H6 and 11B2D6

Ground state rotation and quartic distortion constants were obtained for ¹¹B₂D₆ from the analysis of high resolution (～0.05 cm^?1) Fourier transform infrared spectra. The bands studied comprised the ν₁₇, ν₁₈ type A, and ν₁₄, ν₉ + ν₁₅ type C bands of ¹¹B₂H₆ and the ν₁₆, ν₁₇, ν₁₈ type A, ν₈ type B, and ν₁₄ type C bands of ¹¹B₂D₆. In the case of ¹¹B₂H₆, the authors' ground state data were combined with those of Lafferty et al. obtained from a previous study (J. Mol. Spectrosc.33, 345–367 (1970)) at comparable resolution of the ν₁₆ type A and ν₈ type B fundamentals. Information on the ground state rotational energy manifold of ¹¹B₂H₆ was accumulated up to J = 23, K_a = 18, and of ¹¹B₂D₆ up to J = 32, K_a = 22. This permitted rather precise determination of the distortion constants Δ_J⁰, Δ_JK⁰, Δ_K⁰, although δ_J⁰ and δ_K⁰ proved to be too small (< 10^?7 cm^?1) and were constrained to values calculated from the force field. Sets of upper state parameters were determined for all vibrational levels studied. Although these appear to be essentially unperturbed globally, several localized perturbations were observed and identified.     

Rotational analysis of the B2Σ+ → X2Σ+ system of the aluminum monoxide radical,AlO

Twenty-five bands of the B²Σ → X²Σ system of AlO with 0 ≤ v′ ≤ 9 and 0 ≤ v″ ≤ 6 have been photographed at high resolution. The measured positions of the assigned lines of each band have been fitted by least-squares to obtain estimates of the constants (B′, D′, B″, D″), the band origin, and Δγ_v′,v″, which is the difference of the upper and lower state spin-doubling constants (γ′_v and γ″_v). The parameters from individual bands have been merged to single-valued estimates, as well as to polynomial representations in ($\text{v +}\text{1}\text{2}$). Although the spin-doubling constants are not found absolutely for either state, their vibrational dependences are well determined. The data are employed in the computation of RKR potential energy curves and an array of Franck-Condon factors and r-centroids.     

Diborane: High-resolution infrared rovibration studies of 10B2D6

Studies of five comparatively unperturbed infrared active bands in the spectrum of ¹⁰B₂D₆ were undertaken with a resolution of ca. 0.05 cm^?1. These comprise three type-A bands (ν₁₇, ν₁₈, and ν₅ + ν₁₅), one type-B band (ν₈), and one type-C band (ν₁₄). Ground-state rotational and quartic centrifugal distortion constants were determined for the first time from a total of over 400 combination differences. Sets of upper-state parameters were determined for all five bands studied, and the effects of a number of minor Coriolis interactions between fundamental vibrations are discussed.     

The visible and photographic infrared spectrum of osmium oxide

The emission spectrum of OsO has been photographed in the region 405–875 nm where many new bands have been observed. In favorable cases the ${}^{190}\text{OsO}{}^{192}\text{OsO}$ isotopic splittings have been resolved and aid in vibrational assignments. Three visible bands in the region 433–470 nm have been assigned as (1,0), (0,0), and (0,1) of a $\text{ΔΩ}\text{= 0}$ electronic transition. The (0,0) and (0,1) bands have been rotationally analyzed, yielding principal constants (cm^?1) for the visible system of ν₀ = 22 273.3, B′₀ = 0.3657, D′₀ = 2.8 × 10^?7, B″_e = 0.4023, D″_e = 3.2 × 10^?7, $\text{Δ}\text{G″(}\text{1}\text{2}\text{) = 780.7}$, and $\text{Δ}\text{G″(}\text{1}\text{2}\text{) = 884.9}$. A band at 825.4 nm has been found to be a $\text{ΔΩ}\text{= +1}$ (0,0) band with the same lower state as in the analyzed visible bands. Constants for the upper state of the ir system are ν₀ = 12 109.7, B′₀ = 0.3845, and D′₀ = 3.1 × 10^?7 cm^?1.     

Vibrational spectra and force constants of symmetric tops: Rovibrational spectra in the ν3 region of monoisotopic species of H3GeCl,H3GeBr,and H3GeI

The gas phase infrared spectra of several monoisotopic species of H₃GeCl, H₃GeBr, and H₃GeI have been recorded in the ν₃ region near 420, 300, and 250 cm^?1, respectively, with a resolution between 0.03 and 0.04 cm^?1. Rotational J structure of the fundamental and of several “hot” bands of ν₃ has been resolved and analyzed by means of polynomial methods. The K structure of J clusters is indicated, and α₃^A values were estimated from a band contour simulation. The molecular parameters ν₃⁰, χ₃₃, (B₃-B₀), and $\text{D}{}_{\mathrm{J}}$ were determined for several isotopic combinations. The ν₃ and 2ν₃ levels are apparently unperturbed except for H₃Ge³⁵Cl species for which Fermi resonance between 2ν₃ and ν₂ has been established.     

Rotational analyses and vibrational assignments of the 463- and 474-nm bands of NO2

The excitation spectrum of NO₂ was investigated in the blue region by using a Nd:YAG laser-pumped dye laser. The 463- and 474-nm bands of the ²B₂-²A₁ system were identified and analyzed using the simplification that occurs if the excitation spectrum is monitored at particular wavelengths. Band origins and rotational constants were obtained. Vibrational assignments have been given to these bands by comparing the Franck-Condon Factors calculated for the ²B₂-²A₁ system with the fluorescence intensities of bands going to different vibrational levels of the ground state. The vibrational assignments and molecular constants obtained in this work are (v′₁, v′₂, v′₃) = (3, 11, 0)ν₀(K′ = 0) = 21584.1, $\text{B}\text{= 0.405}$, and $\text{∥}\text{?}\text{′∥ = 0.05}\text{cm}{}^{\mathrm{?1}}$ for the 463-nm band; and (v′₁, v′₂, v′₃) = (2, 12, 0), ν₀(K′ = 1) = 21104.9, $\text{B}\text{= 0.408}$, and $\text{∥}\text{?}\text{′∥ = 0.03}\text{cm}{}^{\mathrm{?1}}$ for the 474-nm band.     

The spectrum of allene near 5 μm

The infrared bands of allene between 1920 and 2028 cm^?1 were measured on a large grating spectrometer with effective resolution of 0.006–0.007 cm^?1 after deconvolution. The main band in this region is the antisymmetric CC stretching fundamental ν₆ of symmetry B₂, accompanied on the high-frequency side by the overtone band 2ν₉ of the degenerate CH₂ rocking vibration. The overtone has three components of species B₂, B₁, and A₁, of which B₂ is in Fermi resonance with ν₆, B₁ has second-order Coriolis interaction with ν₆, while A₁ is in l-type interaction with the B₁ and B₂ components. Additional perturbations by other unobserved states were detected in the spectrum. The observed transitions were analyzed with the aid of a general computer program system SYMTOP designed for analysis of symmetric-top spectra. The main program effects a least-squares refinement of the spectroscopic constants for a set of bands whose upper states interact through arbitrary matrix elements. Two sets of spectroscopic constants for the ν₆, 2ν₉ states were calculated. One, based only on those lines which appear to be unperturbed by unknown and unobserved states, and a second, obtained after inclusion in the H matrix of two perturbing states designed to simulate the effect of the perturbations on all of the data. Comparison indicates that the lower-order constants based merely on the “unperturbed” data are quite satisfactory. Molecular constants for the ν₉ vibration of C₃H₄ are reported.     

Diode laser spectrum of diacetylene near 5 μm

The ν₅ rotation-vibration fundamental band and the ν₅ + ν₉ band of diacetylene in the region 2000–2037 cm^?1 have been measured to an accuracy of better than ±0.004 cm^?1 using a tunable-diode laser spectrometer. The l-type doubling in the (ν₅ + ν₉ ? ν₉ band has been resolved. Line positions, assignments, band origins, and rotational constants B′_v, B″_v, D′_v, and D″_v are reported.     

Cyclopropane-d6: The C–D Stretching Bands ν6and ν8at High Resolution

The two infrared active C–D stretching bands ν₆and ν₈of C₃D₆were recorded on a large Fourier transform spectrometer with a linewidth close to the Doppler–Fizeau limit. The perpendicular band of theE′ vibration ν₈near 2209.6 cm⁻¹is found to be highly perturbed by anharmonic resonances with the states ν₇+ 3ν₁₄, ν₇+ ν₉+ ν₁₄, and ν₄+ ν₁₀+ ν₁₄, and by aJ_x,yCoriolis-type interaction with an unidentified[formula]state. In contrast, the structure of the parallel band of the[formula]vibration ν₆near 2336.7 cm⁻¹appears to be relatively unperturbed. Spectroscopic constants are reported for the two fundamentals and for some of the perturbers of the ν₈state.     

Tunable laser study of the ν10 + ν11 band of cyclopropane

Diode laser measurements of the ν₁₀ + ν₁₁ (l_tot = ±2) perpendicular band of cyclopropane have led to the assignments of roughly 600 lines in the 1880–1920-cm^?1 region. Most of the spectra were recorded and stored in digital form using a rapid-scan mode of operating the laser. These spectra were calibrated, with the aid of a computer, by reference to the R lines of the ν₁ + ν₂ band of N₂O. The ground state constants we obtained are (in cm^?1) B = 0.670240 ± 2.4 × 10^?5, D_J = (1.090 ± 0.054) × 10^?6, D_JK = (?1.29 ± 0.19) × 10^?6, D_K = (0.2 ± 1.1) × 10^?6. The excited state levels are perturbed at large J values, presumably by Coriolis couplings between the active E′(l_tot = ±2) and the inactive A′(l_tot = 0) states. Effective values for the excited state constants were obtained by considering only the J < 15 levels. The A₁-A₂ splittings in the K′ = 1 excited states were observed to vary as q_effJ(J + 1), with q_eff = (2.17 ± 0.17) × 10^?4 cm^?1.     

Intensities of rotational lines in combination bands for axially symmetric molecules of the group C3v

The interaction of vibration and rotation is considered in the computation of the intensities of rotational lines in the combination bands of axially symmetric molecules of the group C_3v. The calculation utilizes the contact transformation method through first order of approximation as outlined by Hanson and Nielsen. General formulas for the intensities of the lines in the parallel combination band (ν_n + ν_n′) and perpendicular combination band (ν_m + ν_n) are obtained. It is found that to this order of approximation the usual selection rules ΔJ = 0, ±1 and ΔK = 0 are observed for the parallel combination band. For the perpendicular combination band the selection rules are more complicated, being ΔJ = 0, ±1, Δl_m = +1 and ΔK = +1 or ?2, Δl_m = ?1 and ΔK = ?1 or +2, Δl_m = ±3 and ΔK = 0. Specific intensity formulas are then given for the (ν₁ + ν₃) parallel and (ν₂ + ν₃) perpendicular combination bands of ammonia.     

Upper and lower bounds of quartic centrifugal distortion constants

Expressions are obtained for the maximum and minimum possible values of the equilibrium centrifugal distortion constants τ_αβγδ for a molecule with given structure and vibrational frequencies. The method of calculation, based on Lagrangian multipliers, is also applied to the empirical centrifugal constants (such as D_J, D_JK, D_K, or Δ_J, Δ_JK, Δ_K, δ_J, δ_K) employed in fitting the rotational structure of spectra. These formulas make it possible to test whether a set of observed centrifugal constants is consistent with the rotational constants and vibrational frequencies. When inconsistencies arise, they are probably due to zero-point vibrational effects. By means of a second method employing inequalities, simpler formulas are derived for wider bounds. These are useful in calculating approximate values of the constants, as a preliminary to deciding which terms to include in the rotational Hamiltonian of any particular molecule.     

The ν2 fundamental vibration-rotation band of T2O

The ν₂ fundamental vibration-rotation band of T₂O vapor has been measured at grating resolution, and the rotational structure has been analyzed. The band center and the values of the rotational constants A, B, and C for the ground state and excited state have been determined. These values are consistent with the data for J through 6, and with extrapolation from H₂O and D₂O.     

Molecular constants for the interacting upper states of the ν1, ν3, 2ν2, ν2 + ν4, and 2ν4 bands in 12CH4

In a previous paper (J.-E. Lolck and A. G. Robiette, J. Mol. Spectrosc.88, 14 (1981)) a theoretical model for the interacting upper states of the ν₁, ν₃, 2ν₂, ν₂ + ν₄, and 2ν₄ bands in methane was described. The present paper summarizes the results obtained, using this model, in a comprehensive analysis of the five bands of ¹²CH₄ through J′ = 12. Values of 80 molecular constants, of which 17 correspond to vibrationally off-diagonal operators, are reported. In addition the computed energy levels of the v₃ = 1 state are compared to the experimental ones and to the result of the previous isolated band approach.     

Analysis of the 2ν3 band of 12CD3F at 5.06 μm recorded under high resolution

The 2ν₃(A₁) band of ¹²CD₃F near 5.06 μm has been recorded with a resolution of 20–24 × 10^?3 cm^?1. The value of the parameter (α^B ? α^A) for this band was found to be very small and, therefore, the K structure of the R(J) and P(J) manifolds was unresolved for J < 15 and only partially resolved for larger J values. The band was analyzed using standard techniques and values for the following constants determined: ν₀ = 1977.178(3) cm^?1, B″ = 0.68216(9) cm^?1, D″_J = 1.10(30) × 10^?6 cm^?1, α^B = (B″ ? B′) = 3.086(7) × 10^?3 cm^?1, and β^J = (D″_J ? D′_J) = ?3.24(11) × 10^?7 cm^?1. A value of α^A = (A″ ? A′) = 2.90(5) × 10^?3 cm^?1 has been obtained through band contour simulations of the R(J) and P(J) multiplets.