The electronic transition spectrum of IrO in the spectral region between 448 and 650 nm has been recorded and analyzed using laser vaporization/reaction free jet expansion and laser induced fluorescence spectroscopy. The IrO molecule was produced by reacting laser-ablated iridium atoms with N(2)O seeded in argon. Five electronic transition systems, namely, the [17.6]2.5 - X(2)Δ(5/2), [17.8]2.5 - X(2)Δ(5/2), [21.5]2.5 - X(2)Δ(5/2), [22.0]2.5 - X(2)Δ(5/2), and [21.9]3.5 - Ω = 3.5 systems were identified. Transition lines of both the (191)IrO and (193)IrO isotopes were observed and analyzed. IrO was determined to have a X(2)Δ(5/2) ground state. A least squares fit of the measured rotational lines yielded molecular constants for the ground and low-lying electronic states. A molecular orbital energy level diagram has been used to help with the assignment of the observed electronic states.

High resolution laser induced fluorescence spectrum of IrB in the spectral region between 545 and 610 nm has been recorded and analyzed. Reacting laser-ablated iridium atoms with 1% B(2)H(6) seeded in argon produced the IrB molecule. This is the first experimental observation of the IrB molecule. Four vibronic transition bands, (v,0) with v=0-3 of an electronic transition system, have been observed. Spectra of all four isotopic molecules, (191)Ir(10)B, (193)Ir(10)B, (191)Ir(11)B, and (193)Ir(11)B, were recorded. Isotopic relationships confirmed the carrier of the spectra and the vibrational quantum number assignment. Preliminary analysis of rotational lines showed that these vibronic bands are with Omega' = 2 and Omega" = 3. The electronic transition identified is assigned as the [16.5](3)Pi(2)-X(3)Delta(3) system. Partially resolved hyperfine structure which conforms to the Hund's case a(beta) coupling scheme has been observed and analyzed. The bond length r(0) of the lower X(3)Delta(3) state of IrB was determined to be 1.7675 A.

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Using the crossed molecular beam method, the yields of the alkali halide product MBr from the exoergic reactions CH3Br+M→MBr+CH3 (M≡K, Rb) have been measured as a function of relative translational energy up to 0.9 and 1.3 eV for K and Rb, respectively. Supersonic seeded beams of CH3Br are crossed with thermal alkali beams and the in-plane angular distribution of MBr measured at different average relative translational energies ?tr. The reactions are found to have appreciable energy thresholds, 0.24±0.06 and 0.20±0.06 eV for the K and Rb-reactions, respectively. The product yields increase monotonically with ?tr above threshold. The postthreshold energy dependence of the cross sections has been obtained by deconvoluting these data from the crossed beam velocity distributions. The MBr angular distributions are characteristic of a direct, rebound mechanism, with a large fraction of the available energy going into product translation. The average recoil energy ?′tr of the product MBr increases linearly with ?tr (d?′tr/d?tr?0.73). The present data for the M+CH3Br systems are compared with previous results for the analogous CH3I reactions and with predictions of several theoretical models. The significantly higher activation barriers for the CH3Br reactions account for their smaller thermal reaction rate constants relative to the analogous CH3I reactions (from early flame experiments).

Electronic transition spectrum of cobalt monoboride (CoB) in the visible region between 495 and 560 nm has been observed and analyzed using laser-induced fluorescence spectroscopy. CoB molecule was produced by the reaction of laser-ablated cobalt atom and diborane (B(2)H(6)) seeded in argon. Fifteen vibrational bands with resolved rotational structure have been recorded, which included transitions of both Co(10)B and Co(11)B isotopic species. Our analysis showed that the observed transition bands are ΔΩ = 0 transitions with Ω" = 2 and Ω" = 3 lower states. Four transition systems have been assigned, namely, the [18.1](3)Π(2)-X(3)Δ(2), the [18.3](3)Φ(3)-X(3)Δ(3), the [18.6]3- X(3)Δ(3), and the [19.0]2-X(3)Δ(2) systems. The bond length, r(o), of the X(3)Δ(3) state of CoB is determined to be 1.705 Å. The observed rotational lines showed unresolved hyperfine structure arising from the nuclei, which conforms to the Hund's case (a(β)) coupling scheme. This work represents the first experimental investigation of the CoB spectrum.