Five simple microwave cavities for producing discharges in gases were tested in He and H2 at pressures from I" to 1 atm. Three of the cavities are commonly used, and two have been recently designed. One of the newly designed cavities offered a considerable improvement over early models with respect to compactness, ease of attachment to the system, and efficiency. T ABLE I. Ca vi ty characteristics. to damage; (3) it produces little electrical interference; and (4) the source presents no dangerous high voltage which can be easily contacted. Many early sources were fashioned from government surplus radar equipment but, usually, considerable knowledge of microwave techniques was required to procure and assemble an adequate system. The need for an inexpensive, uncomplicated source of cw microwave power was finally satisfied to a great extent through the use of medical diathermy units which supply a maximum of about 125 W at 2450 MHz. The usefulness of this power source rests on the proper choice of discharge cavities. It is the purpose of this paper to describe three established and two relatively new cavity

Radiative lifetime and quenching cross section of the B 1π u state of K2 by time correlated single photon counting using a modelocked He-Ne laser J. Chem. Phys. 66, 4509 (1977); 10.1063/1.433703Rotational lifetimes and selfquenching cross sections in the B 3 Π ou + state of 127I2 Fluorescence lifetimes, self-quenching cross sections, and foreign gas quenching cross sections have been measured for 1 2 B 3 IIO u +) by direct observation of fluorescence decay for excitation in the region 640-499.5 nm, corresponding to excited electronic state levels between v' "" 5 and v' "" 70, close to the dissociation limit. The foreign gas experiments represent the first measurement of foreign gas quenching rates using lifetime methods. A pulsed tunable nitrogen-Iaser-pumped-dye laser with a linewidth of 0.3 to 0.7 nm and a pulse time of less than 10 -8 sec was used as the excitation source. Lifetimes were found to be strongly dependent on v', varying from less than 0.4 J.l.sec to greater than 7 J.l.sec. Seif-quenching cross sections showed less v' dependence, varying between 47 and 90 X 10-16 cm 2 • Foreign gas quenching cross sections were measured for Ar, Br 2 , CO 2 , H 2 , He, Kr, N 2 , NO, Ne, °2, SF 6 , and Xe, and showed a dependence on both v' and the gas used. Values for light gases, such as H2 and He, were typically I X 10-16 cm 2 or less, while values for Xe were as high as 23 X 10-'6 cm 2 •

The effect of oxygen, hydrogen, and deuterium atoms and of molecular O2, D2, and SF6 on the vibrational population distribution of N2(B 3Π) in nitrogen afterglows has been investigated for pressures between 0.01 and 2.0 torr. At N2 pressures less than 0.1 torr, these atoms cause preferential population in the lower vibrational levels, and all levels appear to have a high rotational temperature. Emission from the N2 first-positive system is increased by as much as a factor of 60 by the addition of oxygen atoms, and there is a pronounced population maximum at υ′ = 6 with smaller maxima at υ′ = 2, 4, 8, and 12. Hydrogen and deuterium atoms decrease the populations in high vibrational levels and have small population peaks at υ′ = 2 and 12.

Band emission from the Infrared, Orange, and Blue systems of FeO is observed in chemiluminescent flames resulting from the reaction of Fe with O3, N2O, NO2, and discharged O2. Flames are produced at a relatively low temperature (700 K) in flowing inert gas at pressures of 10−3 atm. Bands not previously reported are observed and ascribed to FeO. Reaction of Fe with O2 produces continuumlike emission of unidentified origin; however, laser photoluminescence studies confirm ground state FeO is present. Photon yields for the Orange systems of FeO formed in reactions with O3 and N2O are found to be on the order of 2% and 0.2%, respectively. Photoluminescence of FeO is excited with a krypton ion laser and a cw, tunable dye laser. Ground state vibrational constants of ω″e = 875.8 cm−1 and ω″ex″e = 4.6 cm−1 are determined from the laser excited photoluminescence spectra. Using the tunable dye laser, a rotational constant for the upper state of the B 0,0 band (λ = 579 nm) is found to be B′0 = 0.497 cm−1. Radiative lifetimes of the Orange system upper electronic levels are measured using a pulsed, tunable dye laser excitation source. Lifetimes are found to be on the order of 450±100 nsec.

Absorption spectra from 2200 to 4000 Å have been obtained of chromium, manganese, iron, cobalt, copper, nickel, tin, and palladium atoms trapped in argon matrices at 4.2°K and of iron and copper in krypton and xenon matrices at 4.2 and 20°K. Observed transitions were found to correlate with gas phase transitions, under the assumption of a matrix and atomic configuration dependent shift of the atomic transitions. Energy shifts of the transitions were inversely proportional to matrix atom size. Configurations with an odd number of 3d electrons were shifted less than those with an even number. Within a given configuration, the transitions at higher energies were shifted more than those at lower energies. A Lennard-Jones potential was unsuccessful in generating the observed energy shifts caused by the interaction between the trapped atom and the matrix. Atom diffusion and resultant aggregation within the matrix both during the condensation of the solid from the gas phase and during warming was found to be a significant effect. Oscillator strengths, calculated from observed spectra, were from 10 to 100 times less than gas phase values.