Articles you may be interested inEnergies and electric dipole moments of the low lying electronic states of the alkaline earth monohalides from an electrostatic polarization model J. Chem. Phys. 90, 4927 (1989); 10.1063/1.456589 Model polarizabilities and multipoles for ionic compounds. Alkalineearth monohalides J. Chem. Phys. 89, 1656 (1988); 10.1063/1.455112Dipole moments and potential energies of the alkaline earth monohalides from an ionic modelThe radiative lifetimes for a number of electronic states of the alkaline earth monohalide molecules MX, where M denotes Ca, Sr, or Ba and where X denotes P, CI, Br, or I, have been determined directly from the rate of fluorescence decay with time using a pulsed dye laser as an excitation source. The measured lifetimes in nanoseconds are CaP: 5), where A l' A 2' B, C l' and C 2 denote, respectively, the A 2n 1l2 , A 2n 312 , B 2:2:+, C 2n 112 , and C 2n3/2 states, and where the uncertainties, representing one standard deviation, are given in parentheses. The lifetimes of the caX and SrX states are seen to be quantitatively similar, while those of BaX are quite different. No vibrational dependence of the lifetime for the BaI C 2 state is observed for 0 ~ v' ~ 39. Por other MX molecules the vibrational dependence of the lifetime could not be ascertained because the MX molecule was not produced in a sufficiently wide range of ground state vibrational levels. Various one-electron models for the MX transitions are discussed. It is found that a consistent explanation of the transition moments can be obtained by assuming that the transition is between two nonbonding orbitals centered on the metal atom whose mixing coefficients in terms of a truncated metal atom basis set are adjusted to reproduce a subset of the experimentally determined transiton moments. Por the X, A, and B states of CaX and SrX, the nonbonding orbital is primarily n s 0", n p 11', and n p 0", respectively, in character; for BaX it is suggested that (n -1)d 11' and (n -1)d 0" play an important role in the description of the nonbonding orbital in the A, B, and estates.
Reaction dynamics of Al + O2 → AlO + O studied by a crossed-beam velocity map imaging technique: Vibrotational state selected angular-kinetic energy distributionThe reaction Al + 0, --j AIO + 0 has been investigated by the method of laser-induced fluorescence. Excitation spectra are reported for AIO products formed under single-collision conditions in a "beam-gas" arrangement. The relative vibrational populations (proportional to total cross sections for formation), as well as the relative rotational populations for the v = 0 and v = I vibrational levels, are derived. The rotational distributions are found to differ significantly, with v = 0 having more rotational excitation than v = I. The vibrational distribution is non-Boltzmann, the falloff with v > I exceeding v = I compared to v = O. The observed internal state distributions are compared with those calculated from phase space theory. It is concluded tentatively that the partitioning of the Al + 0, reaction energy among the product modes is not governed solely by statistical considerations. The dynamics of the Al + O 2 reaction are compared with those of the exothermic Ba + 0, and endothermic K + O 2 reactions. From a knowledge of the AIO internal states populated by the Al + 0, reaction and from an estimate of the thermal reactant energies, a lower bound for the ground state dissociation energy of AIO is derived. By combining the present lower bound with the upper bound previously derived from observation of the onset of an AIO absorption continuum, the value D g(AIO) = 121.5 ± I kcallmole is recommended for aluminum monoxide. Direct measurement of the fluorescence decay of the AIO B '~t state as a function of time after excitation by the short (-5 nsec) laser pulse has allowed the determination of the radiative lifetimes T(V' = 0) = lOO±7 nsec, T(V' = I) = 102±7 nsec, and T(V' = 2) = 102±4 nsec, where the error estimates represent three standard deviations.
A laserinduced fluorescence determination of the complete internal state distribution of OH produced in the reaction: H+NO2→OH+NO
The mechanisms and rate constants at 293 K of a number of elementary reactions of the ground state BrO (X211, v" = 0) radical are reported. BrO is found to react rapidly only with other free radicals (NO,O),It is unreactive towards singlet ground-state molecules (H2, CH4, C2H4, C21-16), BrO+H2 +products ; k5< ; BrO + CH4, C2H4, C2H6 +products ; k< 101o-o.Free X atoms (X = Br, C1) (formed by bimolecular disproportionation of 2 XO radicals) are normally present in low-pressure systems containing XO radicals. The possible effects on reaction rates of the coexistence of XO and X are considered.The ground state 10(X211, v" = 0,l) radical, produced by the reaction, * rate constants are in units of cm3 niol-I s-l. 22272228 REACTIONS INVOLVING BrO (x") A N D 1 0 ( x " ) the I 0 radical, which might be expected to be closely analogous to those of the BrO radical. The results show a similarity between the bimolecular disproportionation reaction of two BrO radicals, and the decay reaction of I 0 radicals. Detailed quantitative studies on I 0 using electronic absorption spectrophotometry have proved difficult, but some kinetic data on reactions of this radical have been obtained.The I 0 radical has been identified by means of its absorption band system (425-470 nm) following the flash photolysis of mixtures of I2 and 02.4 Subsequently, this identification was confirmed by rotational analysis of a number of emission bands of the same ~y s t e m . ~ A linear extrapolation of the upper state (A211) vibrational levels led to a value of (176f21) kJ mol-l for the dissociation energy, in good agreement with an earlier estimate of 184 kJ mol-l. No quantitative data on the kinetics of chemical reactions of 10(X211) appear to have been reported, although several workers have reported rapid decay of this radicaL4* l 2
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