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A new method is introduced that allows meteor radars to potentially produce height-dependent temperatures, rather than simply averages over the meteor region. The method is applied to data from the Clovar radar, near London, Ontario, and then a three-way comparison between Rayleigh lidar temperatures, hydroxyl temperatures, and meteor temperatures is undertaken. The three methods prove to be complementary. The OH measurements have good accuracy, but suffer slightly from lack of precise knowledge about their height and the fact that they are effectively integrated over the depth of the OH layer. The lidar temperatures are measured at well-defined altitudes and have better accuracy than the meteor method. The meteor temperatures have the largest errors, but still provide sufficient accuracy for many types of atmospheric studies, and have the advantage that these measurements can be made 24 h a day and in all sky conditions (including during cloud and strong sunlight and moonlight). The measurements from these instruments are complementary in that they are useful for studying the temperature on different time and altitude scales. PACS No.: 94.10.Dy

The polar mesopause region (80-100 km) is the coldest region of the Earth's atmosphere and is expected to be sensitive to global change. Reported increases in observations of polar mesospheric clouds over the last 100 years have been postulated to be related to decreased temperatures (associated with tropospheric warming) and increased water vapour at mesospheric altitudes (a result of increased methane concentrations in the troposphere). The temperature of this region can be monitored by spectroscopic techniques utilising hydroxyl (OH) emissions which originate near 87 km. The Australian Antarctic Division, Atmospheric and Space Physics group has been analyzing OH (6-2) band spectra recorded with a Czerny—Turner scanning spectrometer at Davis Station, Antarctica (68.6° S, 78.0° E) to optimise temperature determinations for climate change studies. A number of difficulties were encountered, some of which have been overcome and all of which can be overcome. The mid-winter average temperature of the OH layer for May-July 1990 has been measured as 224 ±2 K. The equivalent value for 1996 is 215±2 K. Possible reasons for the difference are discussed.

The ability to routinely acquire measurements of the ozone density profile in the mesosphere and lower thermosphere is important for use in chemical-dynamical models of the middle atmosphere. Zenith measurements of the O2(1Δg) (0,1) band emission rate in the evening twilight were acquired near the spring equinox of 1982 with a Michelson interferometer from London, Ontario, Canada. Knowledge of the change of the O2(1Δg) (0,1) band emission rate at twilight can be related directly to ozone density, since ozone destruction by sunlight is the primary source of O2(1Δg) in the atmosphere. Measurements and calculations have shown that a secondary peak in the ozone density often exists in the middle atmosphere. A model has been developed to infer the ozone profile in the middle atmosphere by simultaneously solving the time-dependent chemistry of the molecular oxygen atmospheric and atmospheric-IR bands and O(1D) during twilight. Calculations are presented which show the effect of a secondary peak in the ozone density at various heights on the O2(1Δg) (0,1) band emission rate during twilight. The model is used to demonstrate that the London measurements are consistent with an ozone profile with a secondary peak at 85–90 km.

A very high resolution spectrum is presented of the planetary nebula NGC 7027 over a 200/cm interval centered at 2950/cm, and the features found are described: (1) nebular continuum, (2) atomic recombination lines of H and He II, and (3) three broader emission features of uncertain origin. For the latter the first evidence is presented that the 3.46 micron feature and possibly the 3.40 micron feature are resolvable into a sequence of narrower features. The interpretation of the broader features is discussed in terms of the hypothesis of identification with emission by polycyclic aromatic hydrocarbons. 18 refs.

Relative populations of the vibrational levels ν = 2 to ν = 9 (except ν = 5) of the hydroxyl radical have been determined from observations of the Δν = 2 and 3 sequences of the vibration–rotation bands in the infrared night airglow spectrum using a Fourier transform spectrometer. The observed line intensities were corrected for water vapour absorption using a new technique. The results indicate a population of the upper vibrational levels which is as much as a factor of two lower than that found in other studies. The observed distribution is not consistent with the atomic hydrogen ozone reaction being the sole excitation mechanism in the night airglow unless the quenching and other rates used in our model are in error.

We present initial results of a new technique in which differential cross-section information is obtained by measuring the spectral line shape of emitted lines. We have measured the spectral line shape of the lithium resonance line at 670.7 nm (1s22s2S–1s22p2P) emitted following 5 keV Li+–He collision and compared it to the shape predicted on the basis of measured and theoretical cross sections using the method developed in paper I. Although broadening effects due to the particular experimental conditions used mask the details near the line centre, the shape of the wings of the line suggest that there is a significant amount of large angle scattering. The limitations of this new technique are discussed and it is concluded that, in the present case, cascade contribution to the population of the upper state is the most likely difficulty.

An electric dipole moment function (EDMF) for OH has been derived by combining airglow and laboratory intensity measurements with recent high precision measurements of the dipole moments for v=0,1, and 2. This empirical EDMF shows remarkable agreement with the a priori MCSCF(7)‐SCEP EDMF. However, it differs sufficiently to produce transition probabilities which are in much better agreement with observations than previously available sets.

The population distribution in the rotational levels of the B2Σu+ state of N2+ produced in Li+–N2 collisions has been measured for incident Li+ energies in the range 3 to 10 keV. Boltzmann distributions were found at all energies at rotational temperatures decreasing from 2500 °K for 3 keV excitation to 960 °K for 10 keV. This variation is shown to be consistent with a simple model of the conservation of angular momentum in the collision.

The principal emission in the Earth ’s airglow at wavelengths between 1 and 2 μm is the Av = 2 sequence of the hydroxyl vibration-rotation bands (Gush & Vallance Jones 1955; Shemansky & Vallance Jones 1961). The hydroxyl emission, whose bands extend from the visible region to 4μm, is present in both the day and night airglow and is probably produced by the chemiluminescent reaction between atomic hydrogen and ozone (Wallace 1962) H + 0 3 - > O H (»' < 9) + 0 2. T he application of the multiplex Fourier spectroscopy to the study of this region of the pectrum (Connes & Gush 1960; Gush & Buijs 1964) has increased the resolving pow er attainable by nearly an order of magnitude, making possible the resolution of the rotational structure of the bands and allowing m ore precise determination of the rotational temperature. During the day, the brightness of the hydroxyl bands is exceeded by th at of the infrared atmospheric system of oxygen whose most intense bands are the 0-0 at 1-27 and the 0-1 at 1-58 um .G round-level observations of this system have been limited to the 0-1 band since the 0-0 band is strongly absorbed by the oxygen of the lower atmosphere (Vallance Jones & Harrison 1958).

The absorption due to the v3 band of methane at a wavelength of 3.3 micrometer has been observed in solar spectra taken with a ballon-borne monochromator during its ascent from 13 to 28 km and during the float period at peak altitude until sunset. Measurements of the equivalent widths of the R(5) and R(6) lines were used in a single-layer iterative calculation to determine methane abundance as a function of altitude. The Voigt line profile was used throughout. The mixing ratio obtained during the ascent decreases from 0.9 ppmv (parts per million by volume) at 13km to 0.7 ppmv at 28 km. The variation of equivalent width with solar zenith angle during the float period is interpreted to indicate a rapid decline in mixing ratio above 28 km. (Author)

The absorption due to the ν3 band of methane in solar spectra has been used to deduce the methane content of the lower stratosphere. The spectra were taken from an aircraft flying at altitudes between 10 and 18 km and at latitudes from 18 °N to 66 °N. It is concluded that methane is uniformly mixed up to 25 km with an average mixing ratio of 0.94 ± 0.16 p.p.m.v. No large latitudinal variation of the mixing ratio was observed.

OH(6–2) Q1/P1 and R1/P1 airglow emission intensity ratios, for rotational states up to j' = 4.5, are measured to be lower than implied by transition probabilities published by various authors including Mies, Langhoff et al. and Turnbull and Lowe. Experimentally determined relative values of j' transitions yield OH(6–2) rotational temperatures 2 K lower than Langhoff et al., 7 K lower than Mies and 13 K lower than Turnbull and Lowe.Key words: Atmospheric composition and structure (airglow and aurora; pressure, density and temperature)

We describe a compact, high resolution portable Fourier Transform Spectrometer for use at the Cassegrain focus of an astronomical telescope. The interferometer is dynamically aligned by continuously adjusting the tilt of the fixed mirror under the control of a servo system which monitors laser beams traversing the optical system. Resolution up to 0.02cm-1 can be obtained in the spectral region 0.8 to 3 μm. Examples of astronomical spectra are given.© (1981) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The 3.3-micron spectrum of the planetary nebula NGC 7027 was searched for the R(0) line of the fundamental vibration-rotation band of the molecular ion HeH(+) without detecting it. The upper limit for detection is 3.7 x 10 to the -14th ergs/sq cm per sec, an improvement in excess of 100 over previous published attempts. This limit is low when compared to expectations based on analysis of molecular processes in gaseous nebulas. Likely causes are incorrect radiative association rates or inadequate representation of the nebular size or of the density distribution in the outer boundary of the nebular model used for the flux prediction. 39 references.

An independent absolute flux calibration of the planetary nebula NGC 7027 is presented based on the flux of the Paschen-beta line of hydrogen at 12,818 A. Absolute fluxes are also determined for several other lines in the spectral region from 0.86 to 1.65 microns observed with a resolution of 1.5 per cm, including He I (12,785 and 10,830 A), Paschen-gamma (10,939 A), He II (10,123 A), and forbidden S III (9532 and 9069 A). The results confirm the absolute flux measurement of Miller and Mathews (1972) for the H-beta line and show that there is no accumulated wavelength-dependent error in line strengths extended redward from H-beta. An electron temperature of about 11,600 K is computed from the intensities of the forbidden S III lines for the region of NGC 7027 where sulfur is doubly ionized. Results of an unsuccessful search for three strong lines of HeH(+) in the region from 1.1 to 1.6 microns are also reported which imply that the unidentified feature previously detected near 3.3 microns cannot be due to HeH(+).

A balloon-borne grating spectrometer has been used to study the spectrum of the airglow between 1.8 microm and 3.6 microm and its diurnal variation. The principal features identified are the bands of the Deltaupsilon = 2 and Deltaupsilon = 1 sequences of the vibration-rotation spectrum of OH. The brightness of the 1-0 band at night was measured to be in the range 270-400 kR on two flights. A sudden decrease in the intensity of the hydroxyl bands occurred in morning twilight at a solar depression of 4 degrees and is ascribed to the photodissociation of ozone. The temperature, as indicated by the Q/R branch ratio, rose from 170 K at night to 255 K at noon indicating a reduction in the height of the emitting layer during the day.