Laser Stark spectroscopy of thioformaldehyde in the 10-μm region: The ν3, ν4, and the ν6 fundamentals

The ν₃, ν₄, and ν₆ bands of thioformaldehyde, H₂CS, have been studied using the technique of laser Stark spectroscopy. The H₂CS was produced by the pyrolysis of dimethyl disulfide, and the spectrum was observed using a multipass absorption cell. The band origins are ν₃, 1059.2037 cm^?1; ν₄, 990.1866 cm^?1; and ν₆, 991.0149 cm^?1. The band previously assigned as 2ν₆ has been reassigned as 2ν₂, leading to a value of the ν₂ band origin of ca. 1439 cm^?1. Rotational constants and dipole moments of the vibrational states have been determined.     

Vibrational analysis of the A′1Π state of barium oxide using two isotopes

Barium vapor is reacted with N₂¹⁶O and N₂¹⁸O at 0.7 Torr to produce clearly distinguishable isotopic bands of BaO A′¹Π-X¹Σ in the wavelength region of 320–415 nm. The unique vibrational numbering is determined by measuring the isotopic shift in the bandheads between Ba¹⁶O and Ba¹⁸O. Spectroscopic constants for the A′¹Π state are determined from the present analysis to be ν₀₀ = 17 588 ± 15 cm^?1, ω_e = 442.45 ± 0.3 cm^?1, and ω_ex_e = 1.652 ± 0.009 cm^?1. Uncertainties represent three standard deviations.     

The vibrational numbering and improved constants of the A3Π1u state of I2

The A-X system of I₂ has been recorded in absorption, under conditions of medium resolution, over the region 8000 – 13 400 Å. Bandheads in progressions based on v″ = 6 through 18 have been measured and assigned. A new vibrational numbering for the A state is proposed, which leads to more reliable values for the important constants of the A state: T_e = 10 906 ± 3 cm^?1, D_e = 1641 ± 3 cm^?1, ω_e = 92.5 ± 0.5 cm^?1, ω_ex_e = 1.20 ± 0.08 cm^?1, ω_ey_e = ?0.062 ± 0.006 cm^?1.     

Analysis of the Raman spectrum of SF6

The Raman active fundamentals ν₁(A1g), ν₂(Eg), ν₅(F2g), and the overtone 2ν₆ of SF₆ have been investigated with a higher resolution and the band origins were estimated to be: ν₁ = 774.53 cm^?1, ν₂ = 643.35 cm^?1, ν₅ = 523.5 cm^?1, and 2ν₆ = 693.8 cm^?1. Raman and infrared data have been combined for estimation of several anharmonicity constants. The ν₆ fundamental frequency is calculated as 347.0 cm^?1. From the analysis of the ν₂ Raman band, the following rotational constants of both the ground and upper states have been calculated:

$\text{B}{}_0\text{= 0.09111 ± 0.00005}\text{cm}{}^{\mathrm{?1}}\text{; D}{}_0\text{= (0.16±0.08)10}{}^{\mathrm{?7}}\text{cm}{}^{\mathrm{?1}}$

;

$\text{B}{}_2\text{= 0.09116 ± 0.00005}\text{cm}{}^{\mathrm{?1}}\text{; D}{}_2\text{= (0.18±0.04)10}{}^{\mathrm{?7}}\text{cm}{}^{\mathrm{?1}}$

.     

Vibrational spectra and force constants of symmetric tops: High-resolution spectra of H374Ge35Cl in the ν1ν4 region near 2100 cm−1

The gas-phase infrared spectrum of monoisotopic H₃⁷⁴Ge³⁵Cl has been studied in the ν₁, ν₄ region near 2100 cm^?1 with a resolution of 0.008 cm^?1. Rotational fine structure for ΔJ = ±1 branches has been resolved for both fundamentals. ν₁ (a₁), 2119.977 03(19) cm^?1; and ν₄ (e), 2128.484 65(8) cm^?1 are weakly coupled by Coriolis x,y resonance, Bξ_1,4^y 2.6 × 10^?3 cm^?1, and l-type resonance within ν₄, q₄⁽⁺⁾ ?8.4 × 10^?6 cm^?1, has been observed. An extended Fermi resonance with ν₅^±1 + 2ν₆^±2, which mainly affects the kl = ?14 and ?15 levels of ν₄, has been detected and analyzed. In addition, several weak and local resonances perturb essentially every K subband of ν₄ and some of ν₁, and a qualitative model is proposed to account for the features observed in the spectrum. Disregarding the transitions involved in local perturbations, the rms deviation of the fit to the remaining 2021 lines is σ = 1.34 × 10^?3 cm^?1.     

Infrared spectrum of stannous oxide (SnO)

A tunable diode laser has been used to measure the infrared spectrum of stannous oxide (SnO) in the gas phase between 830 and 868 cm^?1. Measurements of the v = 1-0, 2-1, 3-2, and 4-3 transitions have been made at temperatures ranging from 930 to 1150°C. Over 175 infrared transitions of the nine most abundant SnO isotopic species have been combined with microwave measurements reported by others in a single least-squares analysis of the data to yield a set of eight Dunham coefficients for the X¹Σ⁺ state of SnO. The data have also been fit by a nonlinear least-squares procedure to obtain B_e, ω_e, and the first five Dunham potential constants. The band center for the vibrational transition of ¹²⁰Sn¹⁶O is found at ν₀ (v = 1?0) = 814.70249 ± 0.00027 cm^?1.     

Infrared spectra of AlF3 in solid argon

Three infrared absorptions are assigned to AlF₃ isolated in solid argon: ν₂ = 286.2 cm^?1, ν₃ = 909.4 cm^?1, and ν₄ = 276.9 cm^?1. The multiplet pattern previously reported near 950 cm^?1 is not present in carefully isolated AlF₃. Our spectra do not conclusively rule out a pyramidal structure for AlF₃; however, no infrared absorptions can be confidently assigned to ν₁, the symmetric stretch.     

Laser photoluminescence spectra of the M+S2− species in solid argon at 12K

Matrix reactions of alkali metal atoms with S₂Cl₂ and photolyzed H₂S samples have been examined by laser excitation at 457.9 nm. The strong photoluminescence spectrum from 12 300 to 18 300 cm^?1 exhibited vibrational spacings near 550 cm^?1. Observation of the same ZPL spectrum with two different precursors identified the carrier as Na⁺S₂^?. The vibrational numbering was made possible by the Na⁺³²S³⁴S^? species in natural abundance and from a 33% ³⁴S-enriched sample of S₂Cl₂. The spectroscopic constants ν₀₀ = 19 990 ± 10 cm^?, ω₀″ = 586 ± 2 cm^?1 and ω₀x₀″ = 2.8 ± 0.2 cm^?1 are in excellent agreement with those reported for S₂^? in alkali halide crystals at low temperature.     

A spectrum of rhenium oxide

The arc emission spectrum of the ReO molecule has been photographed in the region 590–860 nm and three bands of a single electronic transition have been rotationally analyzed. The separation of lines of the isotopic molecules ¹⁸⁵ReO and ¹⁸⁷ReO leads to the conclusion that the vibrational assignments for these bands are 1-0, 0-0, and 0–1. It is conceivable that an electronic isotope shift of ～0.08 cm^?1 exists. The following vibrational and rotational data (cm^?1) have been determined: ν₀(0-0) = 14 038.42, $\text{Δ}\text{G′(}\text{1}\text{2}\text{) = 867.85}$, $\text{Δ}\text{G″(}\text{1}\text{2}\text{) = 979.14}$; B′_e = 0.3889, α′_e = 0.0019, B″_e = 0.4257, α″_e = 0.0043. It is concluded that Λ′ ? Λ″ = +1 with Λ″ ≥ 2.     

Measurement and analysis of the infrared absorption spectrum of the 2ν2 band of 12CH4

Approximately 500 infrared absorption lines with room-temperature strengths between 3 × 10^?5 and 1 × 10^?2 atm^?1 were assigned to the 2ν₂ band of ¹²CH₄ in the region from 2930 to 3250 cm^?1. These determine 207 of the 212 upper-state energy levels through J′ = 12 as well as a number of levels with J′ = 13 and 14. All but 17 of the levels with J′ ≤ 12 are calculated to 0.03 cm^?1 or better on the basis of a Hamiltonion that contains Coriolis and Fermi interaction terms coupling the upper states of the five bands, 2ν₄, ν₂ + ν₄, ν₁, ν₃, and 2ν₂.     

The E → B transition (3000–3140 Å) in Br2

The region 3030–3140 Å of the emission spectrum of Br₂ is reinvestigated using sources containing separated ⁷⁹Br₂ and ⁸¹Br₂. The analysis, which spans v′ levels 0–15 and v″ levels 8–31, indicates that the transition in this region is the analog of the E → B system in I₂, and it is so redesignated. The following spectroscopic constants are obtained for the E state of ⁷⁹Br₂: T_e = 49 779.06 cm^?1, ω_e = 150.46 cm^?1, ω_eχ_e = 0.383 cm^?1, B_e = 0.04172 cm^?1, $\text{R}{}_{\mathrm{e}}\text{= 3.20}\text{A}\text{?}$.     

Simultaneous analysis of the 2ν1 and ν1 + ν3 bands and the equilibrium structure of hydrogen telluride

The Coriolis coupled vibration-rotation bands 2ν₁ and ν₁ + ν₃ of H₂Te, which overlap near 4063 cm^?1, have been analyzed by fitting the lines from all of the Te isotopes simultaneously. Using the resulting rotational constants for the ν₁ + ν₃ band and those previously obtained for the ν₁ + ν₂, ν₂ + ν₃, and ν₂ along with the ground state constants, a set of α's was determined. From the α's the equilibrium rotational constants A_e = 6.2515 cm^?1 and B_e = 6.1036 cm^?1 were calculated and then the equilibrium HTeH bond angle of 90°15′ and an equilibrium bond length of 1.658 Å were calculated.     

The 404.5-nm system of the ReO molecule

Observations on the emission spectrum of ReO in the region 375–870 nm are reported. Five bands of a $\text{ΔΩ}\text{= 0}$ system with (0, 0) band at 404.5 nm have been rotationally analyzed and the principal results for ¹⁸⁷ReO are (in cm^?1) ν₀ = 24 709.90, B′_e = 0.3819, B″_e = 0.4252, ω′_e = 874.8₂, and $\text{Δ}\text{G″(}\text{1}\text{2}\text{) = 979.1}{}_2$. Data on the minor isotopic species ¹⁸⁵ReO are also reported. It is suggested that broad rotational profiles found in bands near 842 nm may be due to nuclear hyperfine structure.     

The D′ → A′ transition in Br2

A vibrational and rotational analysis is presented for the D′ → A′ transition (2800–2950 Å) of Br₂. The analysis includes 11 rotationally analyzed bands for ⁷⁹Br₂ and 3 for ⁸¹Br₂, plus bandheads for 70 additional v′-v″ bands of ⁷⁹Br₂, ⁸¹Br₂, and ⁷⁹Br⁸¹Br. The latter include some violet-degraded and spikelike features at the long-wavelength end of the spectrum, which are interpreted and assigned with the aid of band profile simulations. The assigned features are fitted directly to 14 vibrational and rotational expansion parameters for the two electronic states, from which the following spectroscopic constants are obtained: ΔT_e = 35706 cm^?1, ω′_e = 150.86 cm^?1, ω″_e = 165.2 cm^?1, B′_e = 0.042515 cm^?1, B″_e = 0.05944 cm^?1, $\text{R′}{}_{\mathrm{e}}\text{= 3.170}\text{A}\text{?}$, $\text{R″}{}_{\mathrm{e}}\text{= 2.681}\text{A}\text{?}$. The spectroscopic parameters are used to calculate RKR potentials and Franck-Condon factors for the transition.     

High-resolution infrared spectrum of CH2D2: The ν9 fundamental band at 8 u̧m

The infrared spectrum of CH₂D₂ has been recorded between 1100 and 1360 cm^?1 with a SISAM-type spectrometer whose resolution limit is about 0.015 cm^?1 in our spectrum. Some lines have been identified as transitions of the ν₃ parallel band of CH₃D. The band center ν = 1236.2786 ± 0.0010 cm^?1 and a set of upper state constants was obtained for the ν₉ band of CH₂D₂. A perturbation was pointed out in ν₉; nevertheless, all frequencies have been fitted with a standard deviation of 3.8 × 10^?3 cm^?1.     

Vibration-rotation spectra of CH3CN: The ν7 band and its hot bands near 1040 cm−1

Infrared spectra of CH₃CN were measured in the range 170–600 cm^?1 with a Fourier transform spectrometer (0.06 cm^?1 resolution) and several small portions in the range 1020–1065 cm^?1 with a tunable Pb_1?xSn_xTe diode laser spectrometer (0.001 cm^?1 resolution). The ν₇ band was analyzed by taking account of local Fermi resonance with 3ν₈¹, and the following parameters were determined: ν₇ = 1041.8446(15) cm^?1; 3ν₈¹ =1077.88(5) cm^?1; and ∥k₇₈₈₈∥ = 1.98(1) cm^?1. Two hot bands in the ν₇ band region, i.e., (ν₇ + ν₈)² ? ν₈¹ and ν₆¹ ? ν₈¹, were also analyzed, and ν₈ = 365.05(5) cm^?1 and ζ₈ = 0.874(1) were determined by use of the observed transitions of the ν₇ + ν₈ and ν₆ bands.     

Analysis of the 2770-Å emission system in I2

A weak emission spectrum of I₂ near 2770 Å is reanalyzed and found to to minate on the A(1u³Π) state. The assigned bands span v″ levels 5–19 and v′ levels 0–8. The new assignment is corroborated by isotope shifts, band profile simulations, and Franck-Condon calculations. The excited state is an ion-pair state, probably the 1g state which tends toward $\text{I}{}^{\mathrm{?}}\text{(}{}^1\text{S) +}\text{I}{}^{\mathrm{+}}\text{(}{}^3\text{P}{}_1\text{)}$. In combination with other results for the A state, the analysis yields the following spectroscopic constants: T″_e = 10 907 cm^?1, $\text{D}$″_e = 1640 cm^?1, ω″_e = 95 cm^?1, $\text{R″}{}_{\mathrm{e}}\text{= 3.06}\text{A}\text{?}$; T′_e = 47 559.1 cm^?1, ω′_e = 106.60 cm^?1, $\text{R′}{}_{\mathrm{e}}\text{= 3.53}\text{A}\text{?}$.     

Fluorescence spectra of matrix-isolated Se2

Laser induced fluorescence spectra are reported for samples of natural selenium and of the separated ⁷⁸Se and ⁸⁰Se isotopes in Ar and Kr matrices. The B(0_u⁺) → X(0_g⁺) and B(1_u) → X(1_g) systems of Se₂, already known in the gas, are observed by both single photon and biphotonic excitation considerably red-shifted in the matrices. The A(0_u⁺) → X(0_g⁺) emission of Se₂, not observed in the vapor, appears in the matrices with its origin near 15 100 cm^?1. Another system with ν₀₀ = 24 429 cm^?1 and ω″_e = 538 cm^?1 is thought to belong most probably to some polyatomic Se_n molecule.     

Spin-orbit effects in the ground X2Π state and two low-lying excited valence states B2Π and L′2Φ for NO

The potential energy curves and spectroscopic constants B _e , ω _e , ω _e χ _e , α _e , D _e of the six Ω states (X ²Π_1/2, ? 3/2, B ²Π_1/2, ? 3/2 and L ^′2Φ_{5/2,   7/2}) of the NO radical molecule were calculated using spin-orbit multi-configuration quasi-degenerate perturbation theory (SO-MCQDPT). The spin-orbit coupling effect was considered via the state interaction approach with the full Breit-Pauli Hamiltonian. The spin-orbit splitting energy between the X ²Π_1/2 and X ²Π_3/2 states of the NO radical is 129.61 cm^-1, which agrees reasonably well with the experimental value of 123.13 cm^-1. For the B ²Π_{1/2,   3/2} states, the spin-orbit coupling (SOC) splitting energy is 35.99 cm^-1, the corresponding experimental value is 31.7 cm^-1. The SOC splitting value of the L ^′2Φ_{5/2,   7/2} states was calculated to be 103.2 cm^-1. The spectroscopic constants R _e , ω _e , ω _e χ _e , B _e , α _e , D _e are in reasonable agreement with available experimental and theoretical data for the six Ω states.     

Subject index for volume 100

The ν₂ fundamental band of HNCO has been observed for the first time under a resolution of 0.015 cm^?1. The band origin for this NCO antisymmetric stretching vibration is found to be at 2268.893 cm^?1, rather distant from the previously reported value of 2274 cm^?1. Nineteen subbands have been analyzed and term values for both ground and ν₂ states with K up to 4 have been obtained. Effective rotational constants B and centrifugal distortion constants D and H have also been determined. Interactions are observed with 2ν₄ + ν₅ and ν₃ + ν₄. Large perturbations are observed for K = 0 and K = 1 levels of ν₂. Transitions are also seen for three other vibrations, ν₄ + ν₅ + ν₆, ν₃ + ν₆, and 2ν₄ + ν₆.