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High resolution FTIR spectra of CF3 79Br, 12CF3I and 13CF3I have been studied and analysed in the region of the v 1 CF3 symmetric stretching fundamental which is accessible to CO2-laser pumping. Spectra with a resolution of 0.01 cm-1 have been obtained at various temperatures. J clusters were resolved and analysed by polynomial and simulation methods. In 13CF3I a Fermi resonance between v 1 (v eff = 1047.60 cm-1) and 4v 6 0 (v eff = 1049·51 cm-1) has been established. For CF3 35Cl, 12CF3 79Br and 12CF3I the Fermi resonance between v 1 and 2v 5 0 has been analysed semiquantitatively. Further rotational resonances occur in 12CF3I, which could not be assigned unambiguously, but are likely to be due in part to v 3 + 3v 6. The spectra of the v 5 fundamental near 550 cm-1 have been obtained for CF3Br and CF3I at a resolution of 0·05 cm-1. Whereas v 5 appears to be unperturbed for CF3 79Br, for CF3I a Fermi resonance between v 5 and v 3 + v 6 and a rotational resonance of v 5 with 2v 6 have been assigned. A set ...

Temperature behavior of the rotational resonance ( J = 0 → 1, F = 3/2→5/2) transition of CH 3 Cl 35 under various pressures was investigated over a range of 193 ≤ T ≤ 366K using a source-modulated spectrometer to ascertain how the central resonance shifted as the perturbing gas pressure within the absorption cell was varied. Frequency shifts were determined for measured pressures of 1 ≤ P ≤ 30mTorr for the temperature range specified. Experimental results are compared with recent theoretical calculations.

Infrared-microwave triple resonance was applied to microwave spectroscopy of propynal, HCCCHO, in the v 2 = 1 vibrational state. Eleven microwave transitions were newly observed by using a Zeeman-tuned 3.51 μm HeXe laser as the infrared radiation source. The spectrum was analyzed including the 11 transitions previously observed by double resonance. A least-squares fit of the 13 low- J transitions revealed that the rotational constants in the K −1 = 1 states were slightly different from those of the K −1 = 0 states. A higher-order rotational resonance was proposed for explanation of the effect.

Using a H 2 CO molecular beam, a method is first described which permits the observation of rotational transitions ΔJ=±n (n≥1), induced by collisions with the molecules of a target gas. In the case H 2 CO→H 2 CO, selection rules are defined and rotational resonance effects are observed on the differential cross sections for some ΔJ=−1 transitions. It appears that a direct electric field E considerably modifies the H 2 CO cross sections σ J . Using the pair H 2 Co→NH 3 , the study of σ J variations with E shows that the ΔJ=0 transitions become forbidden, when E is intense. The experimental results are compared with the theoretical transition probabilities variations, due to E and calculated in the Born approximation. An experimental method is deduced which permits, by application of an electric field, to select ΔJ=0 transitions on a molecular beam Etude experimentale des transitions rotationnelles ΔJ=±n (n≥1) induites par collision du formaldehyde avec un gaz tampon. Cas du gaz tampon formaldehyde: determination des regles de selection et mise en evidence d'effets de resonance rotationnelle dans les sections efficaces differentielles pour quelques transitions ΔJ=−1. Forte influence d'un champ electrique sur les transitions qui peuvent devenir interdites. Comparaison aux valeurs theoriques des probabilites de transition calculees a l'approximation de Born

The infrared spectrum of fluoroform has been recorded between 480 and 730 cm-1 at a resolution of 0·03 cm-1. The v 6 perpendicular band at 507·8228 (6) cm-1, heavily perturbed by an l(2,2) type rotational resonance, has been analysed in the P and R as well as in the Q branches. The v 3 parallel band at 700·1009 (6) cm-1 has also yielded molecular constants including C″ - C′. Each of these bands is accompanied by hot bands among which v 3 + v 6 - v 6 and 2v 6 - v 6 deserved special attention since both the upper and lower states of these transitions are perturbed.

The earlier measurements on the self-broadening of OCS rotational transitions by Johnson and Slager have been extended. Measurements have been made at constant pressure on seven rotational transitions in the ground vibrational state from $J=3\ensuremath{\rightarrow}4$ to $J=15\ensuremath{\rightarrow}16$ and at dry ice and room temperatures. The data have been interpreted by a simple theory which assumes a constant contribution to line width from dipole-dipole interactions and an additional $J$-dependent contribution from rotational resonance interactions. Empirically determined temperature dependence is introduced for each contribution. This interpretation, when fit to the observed line widths, $\ensuremath{\Delta}\ensuremath{\nu}$ results in the expression $\ensuremath{\Delta}\ensuremath{\nu}=\frac{1815}{T}+0.00321{T}^{\frac{1}{2}}{(J+1)}^{2}{e}^{\ensuremath{-}\frac{\mathrm{hBJ}(J+1)}{\mathrm{kT}}} \mathrm{Mc}/sec$ at 1-mm Hg pressure. The collision diameters for OCS are found to be approximately linear functions of the rotational state and independent of temperature.

Results are presented of the restoration of vertical humidity profiles from terrestrial thermal-radar measurements of atmospheric absorption above the continent and the ocean at a series of wavelengths λ near the rotational resonance of H2O molecules centered to λ=1.35 cm. The restoration of the humidity profiles in this work was accomplished by the method of statistical regularization. The effect of additional physical information and various a priori data on the accuracy of the solution of the problem is discussed. The prospects of restoring a broad class of humidity profiles according to radiometric data are noted.

The relation between the line-width of the 0-3 vibration-rotation band of HCN at 10380 A. and the pressure of the HCN gas, as well as the pressure resulting from the addition of different extraneous gases, was investigated. In the P and R branches of the band a relation was found between the half-line width and the rotational quantum number, J, which differs for the broadening due to self-pressure and the broadening resulting from pressure of extraneous gases. The results could be explained, according to London's theory, in the former case as an effect due to the combined action of rotational resonance alignment, and in the latter case to alignment alone. Measurements made with the addition of DCN suggest that the chain association of the hydrogen bridge bonds also has an effect on the half-width value.

A number of recent review articles have summarized the application of Molecular Rotational Resonance (MRR) spectroscopy to the area of molecular structure determinations and described how these applications have applied to chemistry. This article will briefly review this established area of MRR spectroscopy and describe two developments that offer the promise of expanding the applicability of MRR spectroscopy. The first development was the observation that some large molecules (by MRR standards) give a series of relatively intense, equally spaced bands that can be quickly recorded and assigned. The other development has been in the theory, procedures, and instrumentation required for accurate intensity measurements. These two developments, examples of each, and the implication of each for use by chemists, as well as molecular structure determinations, will be discussed. Spectrometers that are being used for studies in this established area and the two newer areas will be described in the Appendix.

The Coriolis interaction between ν 2 + ν 3 and ν 3 + ν 5 of 12 CH 3 F and the essential l (2,- 1) rotational resonance in ν 3 + ν 5 , have been treated rigorously up to the fourth order of the Hamiltonian. Eighteen spectroscopic constants are necessary to reproduce 820 experimental data with a standard deviation of 0.0013 cm −1 . Parameters of the anharmonic force field have been derived.

The high resolution and resulting high specificity of molecular rotational resonance (MRR) spectrometry, along with the high sensitivity for certain polar compounds suggests its use for the detection and measurement of trace quantities of these compounds in samples of polluted air.

We show that self-broadening of the ammonia inversion lines with J = K can be explained by taking account of the rotational resonance effect.

A remote sensitive SO 2 detection method is proposed that uses the thermal radiation of the millimeterwave rotational resonance. Preliminary result of the experiment of the idea is described.