Accurate measurements of collision-induced absorption by pure nitrogen in the fundamental band near 4.3 μm have been made in the 0-10 atm and 230-300 K pressure and temperature ranges, respectively. A Fourier-transform spectrometer was used with a resolution of 0.5 cm(-1). The current measurements, which agree well with previous ones but are more precise, reveal that weak features are superimposed on the broad N(2) continuum. These features have negligible temperature dependence, and their origin is not clear at the present time. Available experimental data in the 190-300 K temperature range have been used to build a simple empirical model that is suitable for use to compute atmospheric N(2) absorption. Tests indicate that this model is accurate unlike the estimates produced by widely used atmospheric transmission codes.

Several hydrogen peroxide infrared absorption bands have been obtained under 0.2 cm-1 resolution. They demonstrate both doubling due to internal rotation and effects due to the inertial asymmetry. The groundstate rotational constants are found to be: A"=10.068 cm-" B"=0.8740, C"=0.8384. These parameters indicate a wide dihedral angle for H20 2, as proposed in the following structure: 00 bond=1.475 A, OR bond=0.950 A, dihedral angle = 119.8°, and OOH angle = 94.8°.The constants are applied to the microwave data for H20 2 and the deuterated species. The ground-state splitting is found to be 11.44 cm-I , and this, used with the recently reported torsion at 317 cm-I , yields the barriers hindering internal rotation. They are Voi.= 1300 cm-I and V',an,=300 em-I. A simple correlation of the infrared doublings is attempted.

Fourier transform absorption spectra have been obtained between 700 and 7900 cm−1 at a resolution of 0.2 cm−1 for Ar:C2H2 samples codeposited at 12 K with a beam of argon atoms that had been excited in a microwave discharge. Detailed isotopic substitution studies have confirmed that the predominant product species is HC2, which contributes not only the absorptions previously assigned to its two stretching fundamentals but also several weaker absorptions in the 2000–3600 cm−1 spectral region and a prominent, complicated pattern of absorptions between 3600 and 7800 cm−1. The previous assignment of the 3611 cm−1 HC2 absorption as the CH-stretching fundamental is reviewed, and the assignment of an absorption at 2104 cm−1 as ν2+ν3 of ground-state HC2 is discussed. The near infrared absorption band system has been assigned to the Ã 2Π–X̃ 2Σ+ transition of HC2, extensively perturbed by interaction with high vibrational levels of the ground state. The position of the transition origin could not be definitively established. The previous assignment of gas-phase absorptions of HC2 at 3786, 4012, and 4108 cm−1 to ground-state combination bands has been confirmed, and carbon-isotopic data have been obtained for these bands. Because all of the HC2 absorptions observed in an argon matrix must originate in the X̃(000) state and because the observed matrix shifts are relatively small, these studies may provide a map to facilitate more detailed gas-phase studies.

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We present an experimental study of the self- and N(2)-broadened H(2) O continuum in microwindows within the ν(2) fundamental centered at ~1600 cm(-1). The continuum is derived from transmission spectra recorded at room temperature with a BOMEM Fourier transform spectrometer at a resolution of ~0.040 cm(-1). Although we find general agreement with previous studies, our results suggest that there is significant near-wing super-Lorentzian behavior that produces a highly wave-number-dependent structure in the continuum as it is currently defined.