Absorption bands of O2 and OH in a new ultraviolet continuum and in the XeCl laser spectrum

Two excimer lasers of the automatic pre-ionization type have been constructed. To avoid impurities, the two series of condensers were placed outside the discharge chamber. Using one of these devices we have observed a new ultraviolet (UV) continuum from a discharge through a He–O2 mixture at 900 Torr. The continuous nature of this emission was assured by the observation of almost 80 absorption bands of the O2 Schumann-Runge system arising from highly excited vibrational levels and of some OH bands in the A–X system. The same type of discharge through pure He emits no continuum but some OH bands. The time dependence of the light pulses was studied to infer the origin of the continuum. Based on these observations, we show that the strong absorption in the B–X, 0–2 band of the XeCl laser is due to the P11, Q13, and Q13′ lines in the 0–0 band of the OH A–X system; the estimated intensity of this absorption amounting to 5–7% of the total intensity of the XeCl laser. The XeCl spectra were photographed on an E1 quartz spectrograph and in the third order of a 6.65 m grating.

π-π* Absorption Spectrum of Pyridine-D5

The absorption spectrum of π–π* system of pyridine-D5 molecule has been measured in the range 33790–36990 cm−1, on the Hilger large quartz spectrograph. A large number of sharp bands have been measured and analyzed in terms of ground and excited state frequencies which have been compared with the corresponding frequencies of pyridine-H5 molecule.

The π-π* Electronic Absorption Spectra of p-Dibromobenzenes-D4 and -H4

The uv absorption spectra of p-dibromobenzenes-H4 and – D4 have been recorded on a Hilger E1 large quartz spectrograph in the regions 35370–39540 cm−1 and 35340–39470 cm−1, respectively. The assignments of vibronic bands have been made using the results from the two isotopic molecules. Some of the previous assignments have been revised in the light of the data from the present investigations.

n–π* Electronic Emission and Absorption Spectra of o-Fluorobenzaldehyde in Vapor Phase

The electronic emission and absorption spectra of o-fluorobenzaldehyde have been studied. The emission spectrum recorded on a Fuess glass and a medium quartz spectrograph lies in the region 26 668–17 862 cm−1 and the absorption spectrum recorded on a Zeiss Q–24 medium quartz spectrograph lies in the region 30 995–24 610 cm−1. The O—O band has been observed at 26 337 cm−1. The C=O stretching frequency 1733 cm−1 in the ground state and 1355 cm−1 in the excited state is most intense and forms progressions of bands both in the emission and absorption spectra. The observed bands have been interpreted as combinations of the C=O stretching frequency and its multiples with other fundamentals. The transition involved is A‘–A’ ( n–π*).

Electronic Absorption Spectra of Benzylchloride Vapor

The near-ultraviolet absorption spectra of benzylchloride vapor have been photographed on a medium quartz spectrograph. Two systems of bands have been observed, one at 37 115 cm−1 and the other at 41 748 cm−1, which correspond to B2 ↓ A1 and A1 ↓ A1 electronic transitions. The observed spectra have been analysed in terms of fundamentals and overtones.

Observations of Planetary-Nebula Spectra in the Near Ultraviolet

Several dozen spectrograms of about 20 nebulae were obtained with the quartz spectrograph, placed at the Cassegrain focus of the 125-cm parabolic reflector of the Sternberg State Astronomical Institute Crimean Station. Nebulae with intense Balmer continuum were selected. Nearly half of them had not been studied before. Reductions were made for the nuclei spectra, for the differential atmospheric extinction and for the interstellar absorption. The A0 V stars were taken as absolute intensity standards. The work is not yet finished, but the results will be received in a short time.

The decomposition of nitrogen trichloride photosensitized by chlorine

Two transient absorption spectra in the regions of 2400 and 2950 Å, respectively, have been detected as the result of flash photolysing gaseous mixtures of nitrogen trichloride, chlorine and nitrogen. It is established that nitrogen trichloride is a necessary precursor of the spectra and is photosensitively decomposed by the chlorine. Both spectra appeared diffuse when photographed in conjunction with a medium quartz spectrograph. The action of filters on the intensities of the spectra is described. An assignment of NCI and NCl 2 as the carriers of the spectra, and the effects of nitrogen trichloride on the hydrogen-chlorine reaction, are discussed.

The spectrochemical determination of feldspars within the field microcline-albite—labradorite

SummaryTwo spectrochemical methods of feldspar determination are described: one based on the flame spectrophotometer; the other on the quartz spectrograph. For the first method, unknown feldspars are dissolved in a mixture of hydrofluoric and perchloric acids and diluted to 1 : 104. Percentages of Or and An are determined by comparison with dissolved feldspar standards at the same dilution; percentages of Ab are estimated by difference. For the second method, unknown feldspars are burned, unadulterated, in the cathode of the spectrograph arc and a visual estimation is made of the intensities of the following lines: Na5688, Na5683, Ca4455, Ca4435, Ca4425, K4047, K4044, Ca3644, K3447, Na3303, Na3302, and Ca3159. The estimated intensities are then substituted in two empirically determined functions:(ICa4455+ICa4435+ICa4255+ICa3644+ICa3159)−4/3(INa5688+INa5683+INa3303+INa3302)and (3INa5688+3INa5683+2INa3303+INa3302)−43(4IK4047+3IK4044+2IK3447) .From the algebraic values of these two functions, the compositions of the unknown feldspars, expressed as percentages of Or, Ab, and An, are read directly from a chart based on results obtained from feldspar standards of known chemical composition.