Measurements of pressure-induced shifts in the 1-0 and 2-0 bands of HF and in the 2-0 bands of H35Cl and H37Cl

Fourier absorption spectra of HCl and HF measured at room temperature and low pressures were found to show evidence of pressure-induced shifts of the spectral lines at gas pressures of only 10 torr. Self-induced shifts were measured for the HF 2-0 band and for the H³⁵Cl and H³⁷ 2-0 bands. There were also measured in the same spectra shifts in the HF 2-0 band due to HCl and shifts in both HCl bands due to HF, with indications of shift oscillation due to near-resonant dipole-dipole interactions between HCl and HF. Separate measurements were made of pressure-induced shifts in the HF 1-0 and 2-0 bands and in both isotopic HCl bands, using separately argon, neon, nitrogen and carbon dioxide as the perturbing gases.     

Pressure broadening in the 0–4 through 0–7 overtone bands of H35Cl and H37Cl

We have measured the pressure broadening coefficients of a number of rotation-vibration lines in the 0–4 through 0–7 overtone bands of HCl utilizing a Fourier transform spectrometer and a 409 m path length White cell. These data, when included with previous measurements on the fundamental and lower overtone bands, show a systematic variation of pressure broadening with increasing overtone band. This result reflects a change in the collision dynamics between molecules in the upper state of the transition with ground state molecules.     

Absolute frequency measurements of the 0002-0000, 2001-0000, and 1201-0000 bands of N2O by heterodyne spectroscopy

The absolute frequencies of 39 lines in the 00⁰2-00⁰0, 20⁰1-00⁰0, and 12⁰1-00⁰0 bands of N₂O in the range 4300–4800 cm^?1 have been measured by heterodyne frequency techniques. The lines were each measured in Doppler-limited absorption, with a color-center laser as a tunable probe of the N₂O and two stabilized CO₂ lasers as reference frequencies. New rovibrational constants have been fitted to these measurements. Tables of calculated transition frequencies are given, with estimated absolute uncertainties as small as 10^?4 cm^?1. The pressure shifts of four lines have been measured, and the values fall within the range of 0 to ?2 MHz/kPa (0 to ?0.2 MHz/Torr).     

Determination of A0 for CH335Cl and CH337Cl from the ν4 infrared and Raman bands

The ν₄ infrared and Raman bands of CH₃Cl were analyzed simultaneously. A direct fit yielded a complete set of constants for CH₃³⁵Cl, including A₀ = 5.20530 ± 0.00010 cm^?1 and D_K = (8.85 ± 0.13) × 10^?5cm^?1. For CH₃³⁷Cl an incomplete set of constants was obtained from the infrared band, and A₀ = 5.2182 ± 0.0010 cm^?1 was estimated by curve fitting of the Raman spectrum. The resulting equilibrium structure is $\text{r(}\text{CH) = 1.0854 ± 0.0005}\text{A}\text{?}$, $\text{r(}\text{CCl) = 1.7760 ± 0.0003}\text{A}\text{?}$, and <(HCH) = 110°.35 ± 0°.05.     

10-μm sub-doppler laser-Stark spectroscopy of methyl chloride: Analysis of the ν6 bands of the CH335Cl and CH337Cl

About 900 Stark transitions from 70 vibration-rotation transitions in CH₃³⁵Cl and about 400 transitions from 38 transitions in CH₃³⁵Cl in the ν₆ band have been assigned. These data were analyzed simultaneously with previously published microwave data on the ν₆ = 1 state. The fit has a standard deviation of about 2 MHz for the data for both isotopes. The isoptopic shift ν₆35 ? ν₆37 = 0.3766(6) cm^?1. Rotational dependence of the dipole moment was also just apparent at about μ_J = μ_K = 1 × 10^?5 D, and a complete set of molecular constants is given.     

Pure rotational spectra of 32SF535Cl, 32SF537Cl,and 34SF535Cl up to 300 GHz

Pure rotational spectra of the three molecules ³²SF₅³⁵Cl, ³²SF₅³⁷Cl, and ³⁴SF₅³⁵Cl in their ground vibrational states have been observed up to 300 GHz (8 < J < 80). Molecular parameters have been computed with good accuracy for the three isotopic species. The “K-type” splitting characteristic of molecules belonging to the C_4v symmetry group has been clearly seen and measured.     

Temperature dependence of rare gas broadening and shifting of first harmonic lines of H35Cl

Widths and shifts of HCl vibration-rotation lines, pressurized by rare gases, have been measured for the 0–2 band as functions of temperature. The results reported here complement previously published results on the fundamental band. The model of Smith, Giraud and Cooper is used to calculate widths and shifts; good agreement is obtained between experiment and theory. Problems concerning the accuracy of available potential energy surfaces and the calculation of differential cross sections are discussed briefly.     

The emission spectra of H35Cl+, H37Cl+, D35Cl+, and D37Cl+ in the region 2700–4100 Å

The $\text{A}{}^2\text{Σ}{}^{\mathrm{+}}\text{-X}{}^2\text{Π}$ emission spectrum of HCl⁺ has been measured and analyzed for four isotopic combinations. These analyses extend previous work and provide rotational constants for the v = 0–2 levels of the ground state and for the v = 0–9 levels of the excited state. RKR potentials have been determined for both states, although the upper state could not be fitted precisely to such a model. Calculated relative intensities based on these potentials demonstrated that the electronic transition moment must change rapidly with lower state vibrational quantum number. Although considerable caution should be exercised in applying the concept of equilibrium constants to the $\text{A}{}^2\text{Σ}{}^{\mathrm{+}}$ state, the following are the best estimates of these constants (in cm^?1) for the $\text{X}{}^2\text{Π}$ state of H³⁵Cl⁺: B_e = 9.9406, ω_e = 2673.7, A_e = ? 643.7, and $\text{r}{}_{\mathrm{e}}\text{= 1.315}\text{A}\text{?}$. For the $\text{A}{}^2\text{Σ}{}^{\mathrm{+}}$ state of H³⁵Cl: T_e = 28 628.08, B_e ～ 7.505, ω_e ～ 1606.5, and $\text{r}{}_{\mathrm{e}}\text{= 1.514}\text{A}\text{?}$.     

Rotational analysis of the B3Π(0+) → X1Σ+ band systems of 35Cl35Cl and 35Cl37Cl in the chlorine afterglow emission spectrum

The B³Π(0⁺) → X¹Σ⁺ band system of Cl₂, excited by the recombination of ground state $\text{Cl}{}^2\text{P}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ atoms at total pressures near 2 Torr, has been rotationally analyzed in the range 6300–9900 Å. About 30 bands, with 0 ≤ v′ ≤ 6 and 5 ≤ v″ ≤ 14, were investigated, mostly for both ³⁵Cl³⁵Cl and ³⁵Cl³⁷Cl. The band origins and rotational constants for the B state were obtained with the help of the known constants for the ground state. The principal molecular constants (cm^?1) for the B³Π(0⁺) state of ³⁵Cl³⁵Cl are as follows: T_e′ = 17 817.67(3); ω_e′ = 255.38(3); ω_e′x_e′ = 4.59(1); ω_e′y_e′ = ?0.038(8); D_e′ = 3341.17(14); B_e′ = 0.16313(3); α_e′ = 2.42(3) × 10^?3; γ_e′ = ?5.7(7) × 10^?5. The equilibrium internuclear separation is 2.4311(2) Å. The results of Briggs and Norrish on a transient absorption spectrum of Cl₂ assigned as $\text{0}{}_{\mathrm{g}}{}^{\mathrm{+}}\text{← B}{}^3\text{Π}\text{(0}{}^{\mathrm{+}}\text{)}$ are reinterpreted with the present constants.     

Intensities of the v1-bands of 12CH335Cl and 12CH337Cl near 3 μm

Strengths of individual lines in the v₁ fundamental of methyl chloride have been measured at low pressure and at 296.35 K using a Fourier transform interferometer. The band strengths S_v⁰ obtained by fitting these measurements are 85.8±1.0 and 86.6±1.0 cm^-2 atm^-1 for ¹²CH₃³⁵Cl and ¹²CH₃³⁷Cl, respectively. The Q₃-branch appears to be useful for atmospheric detection of methyl chloride.     

Investigation of the reaction 37Cl(n, γ)38Cl

With Ge(Li) detectors the γ-radiation following thermal-neutron capture in natural and in ³⁷Cl enriched targets was studied. A total of 79 γ-lines has been assigned to the ³⁷Cl(n, γ) reaction and 64 of these lines have been placed in a decay scheme of ³⁸Cl. The excitation energies of 24 bound states of ³⁸Cl have been determined with 0.09–1.2 keV errors. The neutron separation energy of ³⁸Cl is 6107.7 ± 0.4 keV. A strong correlation between reduced stripping widths and (n, γ) primary reduced widths was found for the l_n(d, p) = 1 states if, instead of the Weisskopf reduction factor E_γ^?3, a factor E_γ^?1.2 was used.     

The ν6 band of CF235Cl37Cl from IR-MW double resonance

Effective constants for the ν₆ band of CF₂³⁵Cl³⁷Cl have been determined from the analysis of infrared-microwave double-resonance data.     

The ν1 and ν1 + ν2 − ν2 infrared absorption bands of H12CP

The vibration-rotation spectrum of HCP was recorded in the region of the ν₁ band with a resolution of about 0.035 cm^?1. All the data available were combined to calculate spectroscopic constants for the 00⁰0, 10⁰0, 01^1e0, 01^1f0, 11^1e0, and 11^1f0 states.     

Vibrational spectra and force constants of symmetric tops: ν1, ν5, and 2ν5 of CF335Cl and CF337Cl

The gas phase infrared spectra of CF₃³⁵Cl and CF₃³⁷Cl have been recorded in the ν₁ region and 2ν₅ regions with a resolution of 0.09 cm^?1. Additionally the ν₅ fundamental of CF₃Cl, with natural isotopic abundance, has been reinvestigated with a resolution of approximately 0.36 cm^?1. Molecular constants have been evaluated from the observed spectra by means of polynomials and band contour simulation. The possibility of a Fermi resonance between ν₁ and 2ν₅ is discussed.     

Widths and shifts of H35Cl lines in the fundamental band induced by argon and xenon at low temperatures

We have measured, at high resolution (0.024cm^-1), the linewidths and shifts in the fundamental band of H³⁵Cl broadened by argon (up to 5 bars) and xenon (up to 4 bars) at low temperatures (between 298 and 163 K). The experimental results have been compared with calculated data derived from the Anderson-Tsao-Curnutte theory using the Tipping-Herman potential.     

Absolute absorption cross-section measurements of Schumann-Runge continuum of O2 at 90 and 295 K

Laboratory measurements of the absorption cross-section of the Schumann-Runge continuum of O₂ at the temperatures 90 and 295 K have been made in the wavelength region 130-175 nm. The absolute absorption cross-sections at the same temperatures have been measured at several discrete wavelengths through the region. The absolute cross-sections of the O₂ continuum have been used to put relative cross-sections on a firm absolute basis throughout the region 130-175 nm. These recalibrated cross-sections are available as numerical compilations.     

Strengths of (p, γ) resonances in 33Cl, 35Cl and 28Si

Absolute strength measurements have been performed for the E_p = 580 and 588 keV ³²S(p,γ)³³Cl, E_p = 1214keV³⁴S(p,γ)³⁵Cl and E_p = 633 and 744 keV²⁷Al(p,γ)²⁸Si resonances with a Ge(Li) detector. Results are discussed with regard to the decay of isobaric analog resonances in ³⁵Cl and ³⁷Cl.     

Rotation-vibration spectrum of HT: Line position measurements of the 1-0, 4-0, and 5-0 bands

Optoacoustic techniques have been used to determine the line positions of the 1-0 fundamental and 4-0 and 5-0 overtones of the HT (¹H³H) molecule with an accuracy of better than 0.01 cm⁻¹. Comparison with line positions predicted from ab initio calculations that include adiabatic, relativistic, radiative, and nonadiabatic corrections shows disagreement outside of the experimental uncertainties.     

The reaction 35Cl(n,γ)36Cl studied with non-polarized and polarized thermal neutrons

The γ-radiation following capture of non-polarized and polarized thermal neutrons in ³⁵Cl has been investigated. Of the 420 γ-rays ascribed to the ³⁵Cl(n,γ)³⁶Cl reaction, 236 have been placed in a ³⁶Cl decay scheme. The branching ratios and the excitation energies (with 0.04–0.9 keV errors) of 72 bound states have been determined. Unambiguous spin assignments are given for 11 levels. The multipole mixing ratios for some primary γ-ray transitions have been determined. There exists a significant correlation between (d, p) stripping strengths and (n, γ) reduced primary transition probabilities for transitions to l_n(d, p) = 0 levels.     

Vibrational spectra and force constants of symmetric tops: Rotational analysis of ν3 and 2ν3 of H3Si35Cl and H3Si37Cl

The gas-phase infrared spectra of natural and ³⁵Cl isotopically enriched H₃SiCl have been recorded with a resolution of 0.04 cm^?1 in the regions of ν₃ (～550 cm^?1) and 2ν₃ (～1100 cm^?1). The fundamentals of species with ²⁸Si, ²⁹Si, ³⁰Si, ³⁵Cl, and ³⁷Cl and several hot bands of the series nν₃ + mν_i ? mν_i (n, m = 1, 2; i = 3 and 6) have been detected. The parameters ν₀, x₃₃, x₃₆, B₀, α₃^A, D_J⁰ and D_J³ were determined by a combination of least-squares analysis of P and R branches resolved into J peaks (J ≤ 90) and a band contour simulation. Possible resonances of nν₃ and (n ? 1)ν₃ + ν₆ are discussed.