Line oscillator strengths in 16 electric dipole-allowed bands of 14N2 in the 93.5-99.5 nm (106,950-100,500 cm(-1)) region have been measured at an instrumental resolution of 6.5 x 10(-4) nm (0.7 cm(-1)). The transitions terminate on vibrational levels of the 3psigma 1Sigma u (+), 3ppi 1Pi u, and 3ssigma 1Pi u Rydberg states and of the b' 1Sigma u (+) and b 1Pi u valence states. The J dependences of band f values derived from the experimental line f values are reported as polynomials in J'(J'+1) and are extrapolated to J'=0 in order to facilitate comparisons with results of coupled-Schrodinger-equation calculations that do not take into account rotational interactions. Most bands in this study reveal a marked J dependence of the f values and/or display anomalous P-, Q- and R-branch intensity patterns. These patterns should help inform future spectroscopic models that incorporate rotational effects, and these are critical for the construction of realistic atmospheric radiative transfer models. Linewidth measurements are reported for four bands. Information provided by the J dependences of the experimental linewidths should be of use in the development of a more complete understanding of the predissociation mechanisms in N2.

[1] High-resolution, ultraviolet SO 2 photoabsorption cross section data are required for modeling density and temperature profiles of SO 2 in solar system atmospheres. We report measurements of such cross sections on SO 2 at 295 K for theB 1 B 1 -X 1 A 1 and C 1 B 2 -X 1 A 1 bands over the wavelength range 220 to 325 nm. Resolving powers of up to 550,000 were employed in order to study the congested spectrum of sharp SO 2 features in parts of this region. Our data are compared to earlier values obtained with lower resolving power.

A coupled-channel Schrodinger equation (CSE) model of N2 photodissociation, which includes the effects of all interactions between the b, c, and o 1Pi u and the C and C' 3Pi u states, is employed to study the effects of rotation on the lowest-upsilon 1Pi u-X 1Sigmag+(upsilon,0) band oscillator strengths and 1Pi u predissociation linewidths. Significant rotational dependences are found which are in excellent agreement with recent experimental results, where comparisons are possible. New extreme-ultraviolet (EUV) photoabsorption spectra of the key b 1Pi u<--X 1Sigmag +(3,0) transition of N2 are also presented and analyzed, revealing a b(upsilon=3) predissociation linewidth peaking near J=11. This behavior can be reproduced only if the triplet structure of the C state is included explicitly in the CSE-model calculations, with a spin-orbit constant A approximately 15 cm(-1) for the diffuse C(upsilon=9) level which accidentally predissociates b(upsilon=3). The complex rotational behavior of the b-X(3,0) and other bands may be an important component in the modeling of EUV transmission through nitrogen-rich planetary atmospheres.

Abstract. SO2 is an important constituent of the atmospheres of Io and Venus. Accurate photoabsorption cross-section data at the temperatures of these planetary atmospheres are required for the interpretation of SO2 observations and for reliable photochemical models. As part of a planned series of measurements over the 160-300 K range, photoabsorption cross sections of SO2 at 295 K, in the wavelength region 198-220 nm, have been determined from very high resolution (resolving power (X/AX) • 450,000) absorption spectra recorded with a vacuum ultraviolet Fourier transform spectrometer. These new measurements are compared with earlier, lower-resolution (X/AX • 100,000) photoabsorption measurements at 213 K spanning the same wavelength region, with lower-resolution (X/AX = 100,000) measurements at 295 K in a more limited region, and with a recent Doppler-limited laser diode measurement at 295 K over a very narrow wavelength region.

High-resolution laser-based one extreme-ultraviolet ͑EUV͒ + one UV two-photon ionization spectroscopy and EUV photoabsorption spectroscopy have been employed to study spin-forbidden 3 ⌸ u -X 1 ⌺ g + ͑v ,0͒ transitions in 14 N 2 and 15 N 2 . Levels of the C 3 ⌸ u valence and 3s g F 3 and 3p u G 3 3 ⌸ u Rydberg states are characterized, either through their direct optical observation, or, indirectly, through their perturbative effects on the 1 ⌸ u and 1 ⌺ u + states, which are accessible in dipole-allowed transitions. Optical observation of the G 3 -X͑0,0͒ and ͑1,0͒ transitions is reported for the first time, together with evidence for six new vibrational levels of the C state. Following the recent observation of the F 3 -X͑0,0͒ transition at rotational resolution ͓J. P. Sprengers et al., J. Chem. Phys. 123, 144315 ͑2005͔͒, the F 3 ͑v =1͒ level is found to be responsible for a local perturbation in the rotational predissociation pattern of the bЈ 1 ⌺ u + ͑v =4͒ state. Despite their somewhat fragmentary nature, these new observations provide a valuable database on the 3 ⌸ u states of N 2 and their interactions which will help elucidate the predissociation mechanisms for the nitrogen molecule.