Robert Hofstadter

Vibration Spectra and Molecular Structure IV. The Infra‐Red Absorption Spectra of the Double and Single Molecules of Formic Acid

In the present study the absorption spectrum of formic acid vapor between 1 and 15.5μ has been investigated under a variety of temperature conditions. The spectrum at room temperature gives essentially the absorption of the double molecules alone, while that at 140°C gives the absorption of the single molecules. The results are interpreted in terms of the hydrogen bonding existing in the double molecule. In addition an attempt to prepare and investigate pure formic acid‐d is reported.

Vibration Spectra and Molecular Structure V. Infra‐Red Studies on Light and Heavy Acetic Acids

The infra‐red absorption spectra of CH3COOH and CH3COOD between 1 and 15.5μ have been obtained with a rocksalt prism spectrometer. The association of CH3COOD has been studied and a value of the heat of dissociation obtained. Positions of the hydrogen and deuterium bonded O–H–O and O–D–O frequencies are given. Making certain assumptions, a value for the shorter O–H and O–D distances in the dimer rings is found to be 1.07A.

Vibration Spectra and Molecular Structure VII. Further Infra‐Red Studies on the Vapors of Some Carboxylic Acids

The monomer and dimer spectra of the vapors of CD3COOD, CD3COOH, C2H5COOH and C2H5COOD have been obtained in the near infra‐red with a rocksalt spectrometer. The association of C2H5COOD has been studied and the value of the heat of association obtained is 7000 calories per mole per bond.

Vibration Spectra and Molecular Structure VIII. Absorption Spectra of Light and Heavy Phenol and Aniline Vapors

The near infra‐red spectra of light and heavy phenol and aniline vapors have been obtained with a rocksalt spectrometer. Comparisons have been made between the spectra of the light compounds as found in various phases, and an interpretation of certain changes occurring in the spectrum of phenol is suggested. The spectra of the heavy compounds have suggested certain assignments, such as the δ (OD) vibration at 913 cm—1 in heavy phenol and the δ (OH) vibration at 1177 cm—1 in light phenol.

Note on the Detection of Coincidences and Short Time Intervals

A flexible method of detecting coincidences and short time intervals has been devised in which a photo‐multiplier tube views the screen of a cathode‐ray tube. By using one pulse as initiator of a sweep and the other in vertical presentation, coincidences can be observed in a fixed portion of the screen while the remainder of the screen is masked off. In present use the method is limited only by the pulses available (5×10−8 sec.). The method appears to be capable of extension to time intervals of the order of 9×10−10 second or smaller.