Fred L. Mohler

Some Ions of High Kinetic Energy in Mass Spectra of Polyatomic Molecules

When the lighter‐fragment ions of hydrocarbons and hydrocarbon derivatives are recorded with low‐ion accelerating voltages, one observes satellite peaks on the high‐mass side of the main peaks that come from ions with a fairly homogeneous high kinetic energy. Observations of the satellite peaks of CH3+ ions in mass spectra of 13 hydrocarbons and CH3CF3, are reported. The kinetic energies range from 1.5 to 3.4 ev and the relative intensities have a wide range of values but are less than the main peak except in benzene. The appearance potential of the satellite peak is roughly 30 volts in most cases while the main peak is observed above 20 volts. These high‐energy ions are ascribed to doubly charged molecule ions that dissociate into two singly charged fragments. The kinetic energy of the pair of fragment ions is in most cases nearly equal to the Coulomb energy of two ions at a distance equal to the greatest distance between valence electrons in the molecule.

Ionization and Dissociation of Hexafluorobenzene by Electron Impact

Mass spectra and appearance potentials are presented for the principal positive and negative ions of hexafluorobenzene along with comparative data for benzene. Although complete analysis of bond dissociation energies is prevented by lack of thermochemical data, the C–F bond is estimated to be 145 kcal. Qualitatively, the results indicate that C6F6 is thermally more stable than C6H6 and is a relatively stable configuration in the presence of ionizing radiation.

Stages in the Excitation of the Spectra of Thallium

Critical potentials of thallium vapor have been measured with the following results—first resonance potential 0.9 volts, first ionization potential 6.04 volts. A higher critical potential detected by the photoelectric effect of the radiation is at 12.4 volts.Stages in the development of the spectrum were as follows. Below the ionization potential successive lines of the two subordinate series appear with increasing voltage. Above 12 volts another line spectrum appears.Comparison of the critical potentials with the doublet series system of thallium shows that the first ionization potential is determined by the limit 2p2 and the first resonance potential by the difference 2p2–2p1. Since no radiation can result from this transition the orbit 2p1 must be meta-stable. Resonance potentials corresponding to frequencies 2p2–ms and 2p2–md give rise to the observed low voltage spectra. Corresponding critical potentials are computed for Al, Ga and In.The 12.4 volt critical potential and the associated second line spectrum are ascribed to a second type of single ionization, the removal of one of the two 61 electrons.

Calculation of the Luminous Efficiency of Ionized Cesium Vapor

Theoretical computations are given for the radiation and electrical characteristics of the cesium discharge for pressure and power input above the range of present experimental technique. For a given pressure and temperature the electron concentration is given by Saha’s equation, the resistivity depends on the temperature and electron concentration and for sufficiently high pressures the power input is not much greater than the total power radiated by the vapor. The power radiated is evaluated from values of the emissivity times the radiant flux of a blackbody at the vapor temperature. Graphical integration gives the total radiant and luminous flux. An optimum luminous efficiency of about 180 lumens per watt is estimated for a fairly wide range of conditions centering around tube diameter 1 cm, pressure 176 mm, and temperature 6000°K. This requires a current of about 300 amperes and a gradient of 22 volts per cm. The brightness temperature is 5400°K and the color temperature roughly 3700°K. At 760 mm the brightness and color are nearly those of a blackbody. Values for various conditions are tabulated.

The Spectra of Fifth Group Metals

WE have photographed the absorption spectrum of bismuth and also the spectrum of the thermionic discharge at potentials ranging between 4 and 60 volts. Several stages in the excitation of the arc spectrum, and at least two classes of spark lines, have been recognised; 64 arc lines have been classified. The spectrum of the neutral atom is characterised by wide doublets, and most of the energy-levels so far identified are of p-type.