INFRARED SPECTROSCOPY AND KINETICS OF TRANSIENT SPECIES

[摘要] High resolution infrared spectroscopy of transient species produced in a discharge in Ar over polyacetylene and deuterated polyacetylene has been studied using an improved magnetic rotation technique and color center laser probing. Five bands ((0-1), (1-2), (2-3), (3-4), and (4-5)) of the C$sb2$ $bsp 3Sigmasbsp{m g}{-}gets a sp 3Pisb{m u}$ Ballik-Ramsay system, one new band of the ${m Csb 2 H}$ and four bands of the ${m Csb 2 D ilde Asp 2}Pi$-${m ilde X}sp 2Sigmasp +$ system have been identified, assigned and analyzed. Molecular constants for these bands have been accurately determined. In addition, bands of the CN red system, ${m Nsb 2}$ Wu-Benesch ${m Wsp 3}Deltasb{m u}$ - ${m Bsp 3}Pisb{m g}$ system, and CO Asundi $asp{prime 3}Sigmasp+$ - $asp 3Pi$ system have been observed as well as lines due to atomic and ionic Ar. A variety of lineshapes were observed for the various branches and species by magnetic rotation. These lineshapes have been simulated to obtain the peak absorption frequencies by detailed calculations using the ${m Csb 2}$ spectrum as an example. The magnetic rotation technique has proven to be very useful in identifying the assigning spectra because of its unique sensitivity for satellite lines and low J lines and because of the characteristic lineshapes observed. Flash photolysis kinetic spectroscopy has been applied to the ${m ilde Asp 2}Pi$-${m ilde Xsp 2}Sigmasp +$ system of ${m Csb 2 H}$ and ${m Csb 2 D.}$ In this method ${m Csb 2 H}$ and ${m Csb 2 D}$ were produced by photolysing ${m Csb 2 Hsb 2}$ and ${m Csb 2 Dsb 2,}$ respectively, using an ArF excimer laser (193 nm). In addition to the bands seen in magnetic rotation, three new bands of C$sb2$H and four of C$sb2$D with $sp2Sigma$-$sp2Sigma$ symmetry have been identified and rotationally analyzed. The lower states of these bands were found to be the first excited states of the C-C stretch vibration (X(0,0,1)) of ${m Csb 2 H}$ and ${m Csb 2 D.}$ All the upper levels of these bands were found to have rotational constants characteristic of vibrationally excited states of the ground electronic state. All the upper states are severely perturbed. The accurate frequencies of ${m Csb 2 H}$ transitions obtained from high resolution laser spectroscopy have provided a convenient means of direct monitoring ${m Csb 2 H}$ radical in various chemical reactions. The reactions of C$sb2$H with H$sb2$, O$sb2$, NO and C$sb2$H$sb2$ have been studied by direct monitoring ${m Csb 2 H}$ absorption signal using kinetic spectroscopy method. ${m CFsb 3 Csb 2 H}$ was used as a precursor of ${m Csb 2 H}$ in these reactions except for the reaction with ${m Csb 2 Hsb 2}$ where ${m Csb 2 Hsb 2}$ was used both as precursor and reactant. The rate constants of these reactions have been determined to be $4.8 imes 10sp{-13},$ $4.2 imes 10sp{-11},$ $3.5 imes 10sp{-11},$ and $1.5 imes 10sp{-10},$ respectively.

[发布机构] Rice University