Microwave Investigations of Methyl Fluoride, Fluoroform, and Phosphorus Trifluoride

Gilliam, O. R.; Edwards, H. D.; Gordy, Walter

doi:10.1103/physrev.75.1014

Cited by 92 publications

(17 citation statements)

References 14 publications

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“…For an interatomic distance of r= 3.50A and the values of the parameters, A =0.9, B=O.l, a=3 and b=0.2, FIG. 2. Although the damping due to sample spread appears important in (13) at first sight, the effect of the vibrational motion is considerably more important as may be observed from the detailed computation. The shield above the nozzle aperture has several apertures to direct the electron beam various distances away from the nozzle aperture.…”

Section: Finite Sample Sizementioning

confidence: 93%

“…The value of (12) is (13) As the scattering volume is decreased to approach a point source, a and b become large and (13) reduces to the desired function, exp( -(f2)Avs2j2) (sinsr j sr). The value of (12) is (13) As the scattering volume is decreased to approach a point source, a and b become large and (13) reduces to the desired function, exp( -(f2)Avs2j2) (sinsr j sr).…”

Section: Finite Sample Sizementioning

confidence: 99%

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Internal Motion and Molecular Structure Studies by Electron Diffraction. III. Structure of CH2CF2 and CF2CF2

Karle

1950

The Journal of Chemical Physics

119

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The interatomic distances and vibrational amplitudes projected on the lines connecting pairs of atoms at equilibrium have been determined for CH2CF2 and CF2CF2 by an objective procedure for analyzing electron diffraction photographs. Distances involving hydrogen atoms have been evaluated and the procedure for resolving radial distribution peaks involving more than one distance is illustrated. The effects on the accuracy of the method of various characteristics such as sample spread and multiple scattering have been analyzed.

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Section: Finite Sample Sizementioning

confidence: 93%

Section: Finite Sample Sizementioning

confidence: 99%

Internal Motion and Molecular Structure Studies by Electron Diffraction. III. Structure of CH2CF2 and CF2CF2

Karle

1950

The Journal of Chemical Physics

119

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“…In CHaF, the CH distance is 1.109 A, the CF distance 1.385 J... , and HCH angle 110° 0'. The preliminary results for CFaH (16,27), CFaCI (28), CFaBr (29,30), CFaI (29), and CF3CN (29) indicate a carbon-fluorine distance in each of the molecules of about 1.32 J... Cyclobutane is a planar molecule with the symmetry D4b (33). Spectro scopic data have been interpreted to favor a planar configuration also for octafluorocyclobutane (34,35), although recent work has cast some doubt on the earlier conclusions (36).…”

Section: Structuresmentioning

confidence: 92%

“…Phosphorus and arsenic trifiuoride.-The microwave spectra of PFa (16) and AsFa (17) have been measured. Complete structure determinations have not been made, but assuming the FPF angle 104°, the PF distance is 1.546 A, and assuming the FAsF angle 100°, the AsF distance is 1.712 A.…”

Section: Structuresmentioning

confidence: 99%

Experimental Molecular Structure

Roth¹

1951

Annu. Rev. Phys. Chem.

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The principal sources of information about the structure of molecules in the free state are electron diffraction of gases, spectroscopy in the infrared, Raman and microwave regions, and x-ray diffraction of crystals. The past year has seen a continuation of the trends noted in the previous review by Beach (1). The general structural principles for most small molecules are reasonably well understood, and interest now is directed toward the under standing of variations of bond distances and angles in different molecules and the study of more complicated systems, such as larger molecules and the nature of intramolecular motions.The advances in experimental technique in electron and x-ray diffraction and the striking interpretations of pure rotational spectra in the microwave region are beginning to provide a body of information relating to interatomic parameters where the distances are reliable to 0.01 'A or better and the angles reliable to 30'. Some success is obtained in accounting for the observed inter atomic distances by modifying the sum of the covalent radii (14) with cor rections for ionic or multiple bond character (18), but it is apparent that there is a need for precise data from a largernumberof molecules. Accordingly, much of the work at the present time is concerned with improving experi mental techniques or with redetermining the structures of many molecules by the newer methods.Electron diffraction.-The need for the determination of a larger number of parameters has led many workers in the field of electron diffraction to search for increased sensitivity and objectivity. The early electron diffraction investigations were accomplished by the visual correlation technique, where calculated intensity patterns based on assumed models were compared with the visually observed diffraction pattern. As the complexity of the molecules studied increased and it became necessary to determine a larger number of parameters, it became increasingly difficult to arrive at a unique model. At the present time, many molecules are being reinvestigated and extensive work is being done to increase the accuracy and sensitivity of the experimen tal techniques.Recent papers by . the Karles (2, 3, 4) and Hastings & Bauer (5, 8) con tain detailed discussions of the effects of various experimental factors on the diffraction patterns: the proper design of a gas nozzle for introducing the sample into the electron beam, the effect of finite sampJe size and divergence of the beam, mUltiple scattering, the use of beam stops and rotating sectors, and the response characteristics of photographic emulsions.1 This review is a continuation of that of Beach (1) and covers approximately the year 19 50.

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“…The slit was positioned sufficiently far from the end of the shock tube to avoid exposure by radiation behind the reflected shock wave. 4 The lower trace is the simultaneously recorded signal from the monochromator set at 2250 A. The bands observed are listed in Table I.…”

Section: Xenonmentioning

confidence: 99%

Shock Tube Study of Vibrational Relaxation in the A 2Σ+ State of NO

Roth

1961

The Journal of Chemical Physics

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Nonequilibrium NO -y-band emission has been observed behind incident shock waves in rare gas-air mixtures in the approximate temperature range, 5000-10 OOOoK. Vibrational relaxation times for collisional de-excitation of NO(A 22;+) were measured. The measured relaxation times were used to calculate P IO , the probability for collisional de-excitation of the Vi = 1 level of the A 22;+ state; PIO ranges from about 3 X 10-· at 5000 0 K to 3XI0-4 at 10000°K.

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Microwave Investigations of Methyl Fluoride, Fluoroform, and Phosphorus Trifluoride

Cited by 92 publications

References 14 publications

Internal Motion and Molecular Structure Studies by Electron Diffraction. III. Structure of CH2CF2 and CF2CF2

Internal Motion and Molecular Structure Studies by Electron Diffraction. III. Structure of CH2CF2 and CF2CF2

Experimental Molecular Structure

Shock Tube Study of Vibrational Relaxation in the A 2Σ+ State of NO

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