Fluoride Atoms Research Articles

A study of photoreaction of stain films on silicon by infrared spectroscopy

The process of photoreaction of stain films on p-type silicon samples was studied by means of infrared spectroscopy. The stain films were produced by immersion of silicon samples in 0.1 N solution of nitric acid in concentrated hydrofluoric acid. The films contained silicon hydride, silicon fluoride and free silicon atoms at the staining time. During the process of the photoreaction at room temperature, silicon fluoride made hydrogen bond and free silicon atoms turned into silicon oxide. Finally the stain films became silicon oxide, including hydrogen bond Si-O…HO-Si.

Vibrational Spectra of SPCl3, SPCl2F, SPClF2, and SPF3

The infrared spectra of thiophosphoryl trichloride and thiophosphoryl dichlorofluoride in both the liquid and gaseous states, and thiophosphoryl chlorodifluoride and thiophosphoryl trifluoride in only the gaseous state have been recorded from 4000 to 100 cm−1. The Raman spectra have also been recorded for the four thiophosphoryl trihalides in the liquid state and depolarization values measured. Complete vibrational assignments based on band contours, positions, and depolarization values are given. The spectra are interpreted in detail assuming Cs symmetry for thiophosphoryl dichlorofluoride and thiophosphoryl chlorodifluoride, and C3v symmetry for the other two molecules. The vibrational assignment proposed for the SPF3 molecule is in marked contrast to that currently accepted. The P–S stretching vibration is found to decrease in frequency with the increased number of fluoride atoms attached to the phosphorous atom. Possible reasons for the decrease in frequency are discussed.

Relationship between Pi-Electronic Distributions and F19 NMR Shielding in Para-Substituted Fluorobenzenes

Experimental results on F19 shielding in p-substituted fluorobenzenes are combined with calculations of pi-electronic charge distribution from MO theory and are used in several procedures devised to test shielding theories. It is concluded that both —R and +R p-substituted fluorobenzenes represent a special case for which there is a reasonable degree of theoretical justification for relating the F19 shielding with the pi charge density of the fluorine atom. The tests devised for p-substituted fluorobenzenes do not clearly distinguish between the shielding equations of Prosser and Goodman and those of Karplus and Das. Also, the tests do not critically distinguish which of the following may be taken as the better estimator of the pi charge density of the fluorine atom: the shielding parameter based upon unsubstituted fluorobenzene as the standard of comparison or the shielding parameter based upon the meta isomer of the p-substituted fluorobenzene. Data are presented on F19 shielding of the acid fluoride atom of p-substituted benzoyl fluorides and benzenesulfonyl fluorides. These results show that the special shielding relationship derived for p-substituted fluorobenzenes does not apply.

Effect of Temperature on the Intensity of X-Rays Scattered by Powdered Sodium Fluoride

The ratio of the integrated intensities of a number of regularly reflected x-ray lines from powdered sodium fluoride crystals at room and liquid air temperatures has been studied by means of a photographic method. The results of the experiments show that the ratio varies with the angle as predicted by the Debye-Waller formula. The characteristic temperature of sodium fluoride was found to be equal to 442\ifmmode^\circ\else\textdegree\fi{}K. This value agrees as well as one could expect with values calculated by the Lindemann melting-point formula and the known characteristic temperatures of sodium chloride or potassium chloride crystals. Using the known structure factor of sodium fluoride atoms at room temperature and assuming zero-point or no zero-point energy the structure factors of the atoms at rest have been calculated. A comparison with the theoretical structure factors of sodium fluoride and neon (sodium fluoride atoms are neon-like) and with the known experimental structure factor of gaseous neon atoms indicates that the assumption of zero-point energy is correct. The square root of the mean square amplitude of thermal vibration of the sodium and fluorine ions at room temperature was found to be equal to 0.182A.