Observation of spectrally resolved infrared chemiluminescence from vibrationally excited O₃(v₃)

Abstract

Infrared emission from the v3 band of ozone near 9.6/•m has been observed in the COCHISE cryogenic chemical reactor/spectrometer. Vibrationally excited 03, formed principally by recombination of 02 with discharge-produced oxygen atoms at I torr and 80-120 K, is expanded into a low-pressure (~3 mtorr) environment where its infrared radiation is observed without interference from infrared background effects. The observed spectral distributions are interpreted by using a least squares/spectral synthesis method, in which the vibrational state populations and spectroscopic parameters are adjusted in computed spectra so as to provide the best fits to the observed spectra. The (001) --• (000) transition is responsible for most of the observed intensity; however, (/1o3 = 1) emission from higher vibrational levels is also seen, extending to ~ 11/•m (03' -'-6). Although the observed spectral distributions are affected by collisional deactivation occurring in the discharge region, the apparent degree of vibrational excitation observed in these experiments should have considerable beating on investigations of infrared radiation in the upper atmosphere. Recent rocketborne measurements [Nadile et al., 1978] of infrared atmospheric emissions indicate that chemiluminescence in the v3 fundamental band of 03 ((R3)) may be a significant source of 10-12/an radiation in the sunlit atmosphere between 60 and 100 km [Degges et al., 1979]. However, little information exists on the details of the production (R1)-(R2) and loss (R3)-(R4) processes under mesospheric/thermospheric conditions; as a result, it has been difficult and highly speculative to evaluate the role of this mechanism in the upper atmosphere.The formation of vibrationally excited 03 in several modes by (R1)-(R4) has been well established in the laboratory at relatively high pressure and room temperature [von Rosenberg and Trainor, 1973, 1974; however, the extent of excitation was not spectrally defined in those experiments. We wish to report here the initial results from a series of infrared chemiluminescence experiments carried out at lower pressure more representative of the upper atmosphere, utilizing the COCHISE infrared emission spectroscopy facility. The spectral data reported here, which are limited to the •3 band near 9.6 /•m, represent the first laboratory measurements of spectrally resolved infrared emission from vibrationally excited 03. EXPERIMENTALThe measurements were made in the COCHISE facility at the Air Force Geophysics Laboratory, an apparatus described in detail elsewhere [Kennealy et al., 1978[Kennealy et al., , 1979 and which will only be summarized here. This facility provides much-en-

Diurnal variability of vibrationally excited mesospheric ozone as observed during the SPIRE Mission

“…Representative limb spectra between 9 and 12 #m are shown in Figure 1 for selected tangent altitudes in a single, sunlit spatial scan. The characteristic spectral feature which is observed in this wavelength region has the intensity, spectral structure, and altitude dependence expected for the O3(v3) band as previously identified in rocket-borne [Stair et al, 1974;Stair et al, 1983;Rawlins et al, 1985] and laboratory [Rawlins et al, 1981b] measurements. This identification is further borne out by the detailed spectroscopic analysis de- result is obtained from inspection of the SPIRE CO2(¾2) limb radiances at 15 #m [Stair et al, 1985;Caledonia et al, 1985].…”

“…The tailing of the emission to long wavelengths is characteristic of emission from higher-lying vibrational levels of the v3 mode, whose band centers are slightly red-shifted owing to the anharmonic effect. Thus, to analyze the spectral data for populations of individual vibrational levels, we employ a generalized spectral fitting technique [Caledonia et al, 1979; Raw-lins et al, 1981a] previously used on laboratory and field spectra of O3(v) emission [Rawlins et al, 1981b. In the following discussion we use the standard spectroscopic nomenclature for the vibrational quantum numbers of O3(/)1/)2/33), where subscripts 1, 2, and 3 denote motions in the symmetric stretch, bend, and asymmetric stretch modes, respectively [Herzberg, 1945].…”

“…Unfortunately, there is very little detailed spectroscopic information on the higher vibrational states of 03 which would permit the accurate calculation of a spectrum of the type reported here. We have adopted the methods developed for the analysis of similar data obtained in laboratory chemiluminescence experiments [Rawlins et al, 1981b]. These may be summarized as follows.…”

Chemistry of vibrationally excited ozone in the upper atmosphere

“…and band intensity, particularly at such high altitudes. Although some evidence for a similar electron-related O3(v) excitation effect has been seen in laboratory discharges[Rawlins et al, 1981b], none of the reactions we discuss here have been identified or quantified in the laboratory. Indeed, the local 03 number density may actually decrease somewhat due to aurorally enhanced oddhydrogen chemistry, as has been noted in the case of solar proton events[Solomon et al, 1983].…”

“…These were estimated using the anharmonic oscillator/rigid rotor approximation developed for the analysis of COCHISE chemiluminescence data [Rawlins et al, 1981b] and subsequently used in analysis of HIRIS and SPIRE [Green et al, 1985] data. These were estimated using the anharmonic oscillator/rigid rotor approximation developed for the analysis of COCHISE chemiluminescence data [Rawlins et al, 1981b] and subsequently used in analysis of HIRIS and SPIRE [Green et al, 1985] data.…”