Absorption spectra of ClO, BrO, and IO have been observed during the flash photolysis of Cl2–O2, Br2–O2, and I2–O2 mixtures. Rotational and vibrational analyses of the ClO and BrO spectra have been carried out and appropriate molecular constants derived. The transitions are of the type 2Πi(case a)—2Πi (case a). Extensive predissociation has been observed in all three spectra. Theoretical and experimental evidence is presented to show that the excited states dissociate to X(2P3/2) + O(1D). From the observed or extrapolated convergence limits of the absorption spectra the dissociation energies of the ground states are shown to be D0″(ClO) = 63.31 ± 0.03 kcal./mole, D0″ (BrO) = 55.2 ± 0.6 kcal./mole, D0″ (IO) = 42 ± 5 kcal./mole. Mechanisms for the production of the halogen monoxides are discussed and evidence is presented for the participation of excited [Formula: see text] halogen atoms.

The 1–0, 2–0, and 3–0 rotation–vibration bands of HD have been observed with a PbS infrared grating spectrometer and the 3–0 and 4–0 bands have been photographed with a 21-ft concave grating spectrograph. From these spectra precise values of the vibrational and rotational constants of HD in its electronic ground state have been determined. The variation of Bv and ΔG with v is similar to that recently established for H2, that is, the values for v = 0 and 1 are markedly above the values corresponding to a linear extrapolation of the subsequent points. This leads to an uncertainty in the ωe and Be values which is much greater than that of the ΔG and Bv values. The (very low) intensity of the rotation–vibration spectrum of HD is in close agreement with that predicted. The decrease of intensity in going from 1–0 to 4–0 is strikingly slow, far slower than in a normal series of fundamental and overtone bands. This also is in qualitative agreement with theoretical expectation for a molecule like HD which does not have a dipole moment in its equilibrium position.

The "methyl iodide flanle bands", lying in the region 4100 to 6300 a, have been photographed using a 21-ft concave grating spectrograph. The bands are shown to arise from an A211 + X211 transition of the I 0 molecule. Rotational and vibrational analysis of the bands has been carried out and the molecular constants of I 0 obtained. ISTRODUCTION A number of red-degraded bands, now ICIIOWII as the "methyl iodide flame bands", was first observed bl. Vaidya (1937) in emission from a flame of methyl iodide mixed with ~nethyl alcohol or coal gas. The bands were a~~a l y z e d into two systems, A and B, and were tentatively assignecl to the I 0 or CI molecule. Coleman, Gaydon, and Vaidya (1948) obtained the bands in e~nission from all oxyhydrogen flame to which iodine was added, thus supporting the assignment to 1 0 . These authors observed approximately 40 bands in the region 4100 to 6300 A and showed that all the bands could be arranged into one system instead of t~v o . Vibrational constants were given but no rotational analysis was attempted since the b a l d s were observed only ~vith low resolution.Durie ancl Ramsay (1958) observed six bands of the same system in absorption cluring the flash photolysis of mixtures of iodine vapor and oxygen. The bands were observed with high resolution but no rotational analysis of the absorption bands was attempted since the same bancls, extencling to much higher J values, were also observed in emission from an oxyhyclrogen fla~ne to which methyl iodide was added. AlIost of the bands reported by Coleman, Gaydon, ancl Vaiclya were rephotographed under high resolution by Durie and Iiamsay. The rotational and vibrational analysis of these bands forms the main subject of the present paper and confirms the assignment of the bands to the I 0 molecule.The source ~~s e d to excite the methyl iodide flame bands consisted of a diffusion flame of hydrogen, saturated with methyl iodide vapor a t room temperature, burning in an atmosphere of oxygen. The bands were photographed using the second order of a 21-ft concave grating spectrograph ancl Eastman I

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