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Th e extin ction coeffi cie nt of N0 2 has been meas ured in the s pectral ra nge 185 to 410 nm as a f~n c t lOn of te mpe ra ture betw een 235 a nd 298 K. In orde r to correct for the effect of the dimer a bsorptIOn, th e extIn ctIO n coeffi cJe nt of N20 ., ha s .a lso bee n meas ured. The effec t of a decrease in te mpe ra ture upon th e NO t abso rptIOn I S a reductIOn III th e ex tincti on coeffi cie nt of a pproximately 10 pe rce nt in th e range 320 to 380 nm .

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Ketene and diazomethane have been flash photolyzed in their strongest absorption continua in the vacuum ultraviolet and far ultraviolet. Triplet methylene was monitored by kinetic spectroscopy at 141.5 nm. Singlet methylene was not observed directly, but the growth of the triplet absorption as a function of inert-gas pressure indicates that singlet methylene was the major primary product in both the ketene and diazomethane systems. Various inert additives quantitatively quenched the singlet to the triplet state, while reactive additives were able to intercept the singlet before quenching occurred. A number of reactions and deactivations involving singlet methylene (1CH2) and triplet methylene (3CH2) have been investigated at 298°k, and their rate constants are listed below (cm3 molecule·−1 second−1):CH23+3CH2→C2H2+H2 (5.3 ± 1.5) × 10−11 CH21+H2→CH4*→CH3+H (7.0 ± 1.5rparl × 10−12 CH21+H2→3CH2+H2 < 1.5 × 10−12 CH21+CH4→C2H6*→CH3+CH3 (1.9 ± 0.5) × 10−12 CH21+CH4→3CH2+CH4 (1.6 ± 0.5) × 10−12 CH21+He→3CH2+He (3.0 ± 0.7) × 10−13 CH21+Ar→3CH2+Ar (6.7 ± 1.3) × 10−13 CH21+N2→3CH2+N2 (9.0 ± 2.0) × 10−13 CH23+H2→CH3+H < 5 × 10−14 CH23+CH4→CH3+CH3 < 5 × 10−14. The absolute reaction rates for the singlet are apparently independent of the source (i.e., ketene or diazomethane), suggesting that the reactions occur via vibrationally cold singlet methylene. No evidence was found for deactivation of the triplet to the singlet, indicating that the energy difference between the two states is greater than kT (T = 298°K).

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.