The note describes the design and operating parameters of a CO2 laser producing 20 W c.w. power at 10?6 ?m from a discharge 10 cm long and 7 mm diameter.

The character of the electronic states and transitions between them of the astrophysically important molecule ZrO are reviewed. Franck-Condon factors and r centroids, calculated on the basis of a Morse model, are displayed, with wavelengths of known bands, for the α, β, γ, A and B band systems.

A method is descrined for the determination of band strengths from intensity measurements of an optically thick band spectrum in which the bands may be strongly overlapped. Synthetic band intensity profiles are calculated and used to obtain both a temperature, and a well defined value of No¦Re(rv′,v″)¦2 for each band from experimental intensity ratios only. The procedure is applied to the B1∑-X1∑ transition of BeO excited in a shock tube.

The absorption spectrum of AlO has been observed in the wavelength region 2000-3000 Å using a shock tube. Discrete band absorption and continuous absorption were observed. It is suggested that the continous absorption is a dissociation continuum of AlO and its long-wavelength edge gives a value of 4 54 ± 0.01 eV for the dissociation energy.

The time-resolved light output of a shock wave through an oxidizing gas containing powdered aluminum, magnesium, and lead has been studied. The shape of the light pulse has been found to be dependent on the position of introduction and on the nature of the powdered solid. The results indicate that the shock-wave particle interaction is best explained by a combustion model rather than by the more normal ablation mechanisms.

Relative band strengths have been measured for some 40 bands of the Nitrogen Second Positive System excited in a D.C. discharge with a wide range of current densities (0·5–1500 mA/cm2). The results are interpreted as showing a small variation of band strength with current density for this system.

Photographic intensity measurements have been made on the A 2Σ-X 2Σ system of AlO excited in a shock tube and by exploding an Al foil. The electronic transition moment was found to have the form Re(r) = const(1-0.46r). This result confirms that previously reported by Hébert and Tyte for the system excited in an a.c. arc.

IN recent years there has been renewed interest in the spectrum of AlO. The well-known very strong blue-green (A2σ–X2σ, ground-state) system has been re-investigated1,2, and the ultra-violet system (B2Π–X2σ) has also been the subject of new investigations3.

Abstract : Photographic intensity measurements have been made on the A2&-X2& system of A10 excited in a shock tube and by exploding an Al foil. The electronic transition moment was found to have the form R(r) = const (1-0.46r). This result confirms that previously reported by Hebert and Tyte for the system excited in an a. c. arc. (Author)

Relative integrated band intensities of 29 bands of the blue-green system of aluminium oxide, excited in a low pressure arc, have been measured by photographic photometry. The electronic transition moment was found to have the form Re(r) = const. (1-0.46 r); 1 50 Å

The nitrogen first negative system was excited in a cooled discharge through a helium-nitrogen mixture. Some new bands of the system have been observed and the 10-6, 10-7, 10-8, 10-9, 11-6, 11-7, 11-10 bands have been analysed. A perturbation of the X2Σ, ν = 7, level has been observed. A suggestion is made to explain the gap in the Deslandres table of the observed bands of the system.

Integrated band intensities of the second positive system (C3II-B3II) of N2 have been measured photoelectrically. They have been used to test the range of conditions under which the theory normally used in interpreting such measurements is applicable. They have also been used in a new determination of the variation of the electronic transition moment with internuclear separation. The variation of the population of the C3II state with current has been determined and used to identify the probable excitation processes.