John W. McConkey

Absolute cross sections for electron excitation of the second positive bands of nitrogen

Absolute excitation cross sections for the emission of the second positive bands of nitrogen under electron impact have been obtained. Peak level cross sections for the νprime = 0, 1, 2 levels of the c 3IIu state were found to be, respectively, 235 × 10-18 cm2, 144 × 10-18 cm2 and 49 × 10-18 cm2. Good agreement is found with the theoretical A coefficients for the relative intensities of the different vibrational bands. The results are compared with those of other workers and various secondary effects which were observed are discussed.

Electron impact excitation of the B 3capital Πg state of N2

Absolute excitation cross sections for the emission of the first positive bands of nitrogen under electron impact have been obtained. The maximum total cross section of the B 3capital Pig level was found to be 659 × 10-18 cm2. From measurements made on the cascade contribution from the D 3Σu level an approximate maximum cross section for excitation of this level of 3 × 10-18 cm2 was obtained. Other cascade features were observed and discussed. The results are compared with those of other workers.

Absolute cross sections for ionization and excitation of CO2 by electron impact

Absolute cross sections for simultaneous ionization and excitation of CO2 by electron impact have been measured using a crossed-beam technique. The maximum value of the cross section of the B 2Σu+ level is 224 × 10-18 cm2 and that of the A 2capital Sigmau+ level is 744 × 10-18 cm2. Relative cross sections within the vibrational bands are given. The excitation functions are similar in shape to the total ionization function.

Excitation of the A2πu state of N2+ by electrons

Absolute values of the emission cross sections for five vibrational bands in the Meinel system of N2+,A2πu to X2Σg+, excited by electron impact are presented. From these, a value was obtained for the total excitation cross section of the A2πu state at 100 eV of 26·5 × 10−18 cm2. The results are compared with those of other workers and with theory. Collisional transfer of the excitation energy from the levels of the A2πu state was also observed with a transfer cross section of approximately 10−14 cm2.

Optical Line-Absorption Techniques for Measuring Atomic-State Populations

Two techniques are described for the measurement of atomic-state densities by self-absorption within a discharge. One is a variation of a previous method in which a mirror is used to reflect light back through the discharge to the detecting monochromator. This is mainly suitable for use in the visible spectral region. The other technique depends on a comparison of the signals obtained when different lengths of the discharge are excited. It is especially useful in the vacuum. Results are presented to illustrate the two methods.

Excitation of O2+ bands by electron impact

Absolute excitation cross sections for the emission of the first negative bands of O2+ under electron impact on O2 have been obtained. The peak cross section for the b 4?g- state was found to be 32?5 ? 10-18 cm2 at 100 eV. The results are compared with proton and other electron impact data. Some preliminary results on the second negative system are also given.

Influence of metastable helium on the laboratory excitation of O(1D)

Abstract The excitation of the 1D state of atomic oxygen has been studied in an oxygen helium discharge which is a strong source of the forbidden oxygen lines. Collisional deactivation by oxygen molecules is the predominant de-excitation mechanism of the O( 1 D) atoms and the predominant excitation mechanism is shown to be via the collision of metatable helium atoms and ground state oxygen molecules. A rate coefficient of 10−12 cm3 sec−1 is obtained for this reaction.

Absolute transition probability measurement for the electric quadrupole 5577 Å auroral green line

Abstract The transition probability of the 5577 A ( 1 S 0 — 1 D 2 ) line of oxygen has been ob- tained absolutely by simultaneous measurement of the number density of O( 1 S 0 ) atoms in an oxygen-helium discharge and the intensity of the emitted 5577 A line. The experimental technique is described in detail. The value obtained for A-5577 of 1.0 sec−1 is in agreement with theoretical predictions though large systematic and other errors result in a possible inaccuracy of a factor of two.

New emissions of atomic nitrogen in the 10 000–11 000 Å region

Abstract Fifteen new lines of atomic nitrogen have been recorded in the wavelength range 10 412 A -10 761 A and classified as 2 s 2 2 p 2 ( 3 P ) 3 d −2 s 2 2 p 2 ( 3 P ) 6ƒ transitions.

Angular distributions of ions resulting from electron impact on the rare gases

Anisotropies have been observed in the angular distributions of ions resulting from electron impact on the rare gases. This work complements the measurements on the angular distributions of scattered electrons resulting from the ionization process.