D. Krankowsky

Measurement of heavy isotope enrichment in tropospheric ozone

Tropospheric ozone samples collected during a twelve-month period in urban air show an enrichment of about 9% in the heavy isotope 50O3 consistent with predictions from laboratory measurements. The enhancement of about 7% observed in 49O3 is still within the uncertainty of the expected value. These measurements confirm that the isotope effect, repeatedly found in laboratory experiments, is also produced in the atmosphere during the ozone formation process.

Stratospheric ozone isotope enrichments - revisited

Ozone isotope data for 49O3 and 50O3 are presented, that were obtained from 28 stratospheric samples collected over 10 years onboard balloon payloads. Enrichments for 49O3 range from 7 to 9% in the middle stratosphere. This is in very good agreement with laboratory-derived isotope predictions. For 50O3 most enrichments are between 7 and 11%, a few, however, are too high to be of atmospheric origin. Arguments are presented that stratospheric ozone isotope data are consistent with enrichments determined in laboratory studies when pressure and temperature dependence of the isotope effect is included. Results from recent remote sensing experiments support the values obtained during balloon-borne sample collections. Very high enrichments occasionally measured in the past should be disregarded.

Relative formation rates of 50O3 and 52O3 in 16O–18O mixtures

Tunable diode laser (TDL) and mass spectrometry have been combined to measure relative formation rate coefficients of each of the four channels contributing to ozone of mass 50 u and 52 u produced in 16O–18O mixtures. Only one channel has a large rate coefficient advantage causing almost exclusively the observed isotope enrichment. Collisions to form ozone are end-on reactions. Molecular symmetry plays no apparent role in the ozone isotope enrichment process, regardless, whether or not ozone is produced in collisions with homo- or heteronuclear molecular oxygen. The oxygen isotope exchange process may hold a key in explaining the rate coefficient results.

Isotopic measurements of stratospheric ozone

Isotope ratios of stratospheric ozone samples collected during four balloon flights are reported. In an altitude range between 22 and 33 km all ratios show enrichments between 7 and 11%, somewhat lower for 49 O 3 than for 50 O 3 . Those enrichments are in very good agreement with results from laboratory isotope studies when stratospheric pressure and temperatures are included. The new data presented do raise questions about past stratospheric ozone isotope measurements which sometimes showed high values never observed in the laboratory or tropospheric environment.

Density and temperature structure over northern Europe

Abstract During the Energy Budget Campaign, a number of profiles of the density and temperature were obtained to study the structure and variability of the atmosphere. The measurements were made using rocket- borne instrumentation launched from Esrange, Sweden, and Andoya Rocket Range, Norway, during November and December 1980. The techniques included meteorological temperature sondes, passive falling spheres, accelerometer instrumented falling spheres, density gauges, mass spectrometers and infrared emission experiments. The instruments provided data covering the altitude range from 20 to 150 km. The measurements were made during periods which have been grouped into three categories by level of geomagnetic activity. Analysis has been made to compare the results and to examine the wave features and variations in the vertical profiles for scales ranging between hundreds of meters and tens of kilometers. Most of the features observed fit qualitatively within the range expected for internal gravity waves. However, the features in the profiles during one of the measurement periods are unusual and may be due to aurorally generated shock waves. The geomagnetic storm conditions caused temperature increases in the lower thermosphere which maximized in the 120–140 km region.

First simultaneous measurements of neutral and ionized iron densities in the upper mesosphere

We report on the results of a multi-instrument study of a sporadic Fe layer and a sporadic E layer which took place in the night of September 20, 1991, at the Andoya Rocket Range (69°N, 16°E). A ground-based lidar was used to measure mesospheric Fe densities, while simultaneously rocket-borne probes and an ion mass spectrometer measured the profile of total ion density and ion composition, respectively. All instruments observed the sporadic layers near 97 km altitude. Radar tracking of chaff clouds established the wind field in the 90- to 100-km region with high spatial resolution, while the EISCAT incoherent scatter radar measured the E fields in the F region. The major ion in the sporadic E layer turned out to be Mg+. The narrow Fe+ layer was 1 km lower than the sporadic Fe+ layer. The ratio of densities [Fe+]/[Fe] in the peaks of the sporadic layers was found to be 1.75.

Venus Thermosphere: In situ Composition Measurements, the Temperature Profile, and the Homopause Altitude

The neutral mass spectrometer on board the Pioneer Venus multiprobe bus measured composition and structral parameters of the dayside Venus upper atmosphere on 9 December 1978. Carbon dioxide and helium number densities were 6 x 106 and 5 x 106 per cubic centimeter, respectively, at an altitude of 150 kilometers. The mixing ratios of both argon-36 and argon-40 were approximately 80 parts per million at an altitude of 135 kilometers. The exospheric temperature from 160 to 170 kilometers was 285 � 10 K. The helium homopause was found at an altitude of about 137 kilometers.

Isotope dependence of the O+O2 exchange reaction: Experiment and theory

The isotope dependence of the O+O2 exchange reaction is investigated by means of kinetic experiments and classical trajectory calculations on an accurate potential energy surface. The measurements confirm the previously reported negative temperature dependence and yield the rate coefficients for both the exothermic 18O+16O2→18O16O+16O and the endothermic 16O+18O2→16O18O+18O reaction between 233 and 353 K: k8=(3.4±0.6)×10−12 (300 K/T)1.1±0.5 cm3 s−1 and k6=(2.7±0.4)×10−12 (300 K/T)0.9±0.5 cm3 s−1. In addition, the ratio of these two rates, R, has been measured with comparatively higher precision. It is 1.27±0.04 at 300 K and also shows a distinct negative temperature dependence. Four types of classical trajectory calculations are performed in order to interpret the experimental result. They differ by the way in which the quantum mechanical zero-point energy of the reactants and the differences of zero-point energies between reactants and products, ΔEZPE≈±22 cm−1, are phenomenologically incorporated. Only c...

Concentrations of H2O and NO in the mesosphere and the lower thermosphere at high latitudes

Abstract Water vapour and nitric oxide concentrations in the mesosphere and lower thermosphere were derived from infrared emission and positive ion composition measurements above northern Europe during the Energy Budget Campaign 1980. The experiments were performed at different levels of geomagnetic disturbance. Both water vapour and nitric oxide are highly variable. Water vapour mixing ratios between 0.2 ppm and 10 ppm were observed. The nitric oxide peak densities varied by more than a factor of ten. Maximum values of 2 × 10 9 cm −3 were obtained.

Heavy Ozone--A Difficult Puzzle to Solve

Although not abundant, ozone is one of the most important constituents of the atmosphere. The isotopic variants of ozone, which is a symmetric triangular molecule made of three oxygen atoms, are difficult to explain by theoretical analysis. In their Perspective, Krankowsky and Mauersberger discuss results published in the same issue by Gellene (p. 1344) that shed light on the mechanisms responsible for the heavier isotopes of ozone.