Absorption and photoionization coefficients have been measured for H2CO in the 600–2000-Å region. Integrated oscillator strengths were determined for a number of strong Rydberg transitions above 1200 Å. From the photoionization curve the first adiabatic ionization potential was found to be 10.87±0.01 eV. As an aid in interpreting the absorption spectrum, theoretical calculations were made using a single-configuration self-consistent field procedure for the Rydberg states and a model which included mixing between the Rydberg and valence states. On this basis, weak absorption features between 1340 and 1430 Å have been assigned to the B11(σ → π *) valence state. The 1A1(π → π *) valence state is deduced to be strongly autoionized just above the 2B2 ionization limit.

The purpose of the Balloon Ozone Intercomparison Campaign (BOIC) was to assess the accuracy and precision of various ozone measurement systems under development and those flown operationally. Ozone observations made by in situ UV absorption photometers from four groups, two solar UV absorption photometers, three varieties of electrochemical sondes, and a mass spectrometer were intercompared in three flight missions, each involving several balloon flights. Concurrent Umkehr and satellite observations were also intercompared. The National Bureau of Standards (NBS)provided a reference ozone source for intercomparing several of the in situ instruments at ground pressure. Harvard University and the University of Minnesota each developed a calibration facility after the BOIC flights which enabled a comparison of the flight in situ photometers under simulated stratospheric pressure and ozone concentrations. The following is a summary of results. The standard deviation of the sensitivities among 18 instruments tested about the NBS reference was 11%. These differences appear in flight at the lower altitudes, but they change at higher altitudes, indicating height dependent errors, particularly for the electrochemical sondes. Comparisons at the two laboratory facilities simulating stratospheric conditions indicated differences of about 2% at 3 mbar for two of the flight in situ photometers. Ozone values among four in situ UV photometers flown together had a standard deviation about the mean value of about ±3% from the tropopause to about 41 km. This is very close to the expected accuracy of these measurements and therefore is an excellent result. However, during float at 42 km the difference nearly doubled. Experiments performed during flight demonstrated that even near 40 km, wall losses in three UV photometers were less than 5%, which is consistent with the laboratory simulations. A comparison of a complement of electrochemical sondes yielded results that agreed with the mean of the in situ UV photometers to within 0–20%, depending on the sonde type and altitude. The electrochemical sondes gave systematically lower ozone values at pressures lower than 10 mbar (above 31 km). A comparison between an in situ UV and a solar absorption photometer indicated a 10% difference in the stratosphere, where the in situ measurement was lower. Comparisons of electrochemical sondes and Umkehr and Solar backscattered ultraviolet (SBUV) satellite observations showed agreement to within their error bars (stated to be about 5–10%). In two comparisons between in situ UV photometers and satellite measurements, a consistent difference occurred between 10 and 3 mbar (28–40 km), implying a possible bias between the measurement types. Intercomparisons among all the instruments in the troposphere showed 20–30% differences from the mean. A comparison of pressure measurements performed by several experimenters resulted in differences as high as ±15% from the average measurement.

High energyresolution studies of electron impact optical excitation functions. II. The first positive system of N2The emission spectrum of atomic nitrogen (NI). singly ionized atomic nitrogen (NIl). atomic oxygen (01). singly ionized atomic oxygen (011). and molecular nitrogen (N 2 ) dominates the day airglow and aurora spectrum in the extreme ultraviolet. However. analysis of the excitation of these lines is not possible due to the lack of laboratory or theoretical data for the relevant processes. Absolute emission excitation cross sections resulting from low energy electron impact on N2 and O 2 have been measured in the extreme vacuum ultraviolet (500-1200 A). Electron energies were from 0 to 300 eV. Numerous bands of N2 were found between 800 and 1000 A. These band systems are of particular interest because their optical oscillator strengths are unusually large and should have large emission cross sections. Excitation functions were measured for the N, c' II.+ 0 -+ X II tv' = 0 -v· = 0 band emission. the NIl 916 A multiplet. the 01 879 A multiplet. and the 011 834 A multiplet. In addition. cross sections were measured at 200 eV only for several of the band emissions plus the

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Absolute excitation functions for excited fragments resulting from electron bombardment of H 2 0, NH3, and C.H4 by low. energy electrons (0-300 eV) have been measured in the VUV (1100-1950 A).The predommant emISSIOn for each molecule was the H Lyman-a line while the 01 NI CI and C II emissions were at least an order of magnitude weaker. Absolute cross sections ~t 1 00 ~V are given along with the appearance potential of the various processes and the possible dissociative-excitation channels through which such processes proceed.