THE 1B2(ΠΠ∗)←1A1^{1}B_{2} (\Pi\Pi^{*}) \leftarrow ^{1}A_{1} ELECTRONIC BAND SYSTEM OF TOLUENE

Author Institution:The $^{1}B_{2}(\Pi \Pi ^{*})\leftarrow ^{1}A_{1}$ electronic band system of the normal isotope of toluene has been photographed and measured at high resolution. Analysis of the strong vibronic components has led to identification of active $^{1}B_{2}$ state fundamentals. The rotational definition of the strong bands near the origin, $\nu_{00} = 37478.76 cm^{-1}$, suggests that a band contour computation including internal rotation of the methyl group should be attempted. Preliminary results of such as asymmetric top/internal rotation computation will be presented

IDENTIFICATION OF TORSIONAL TRANSITIONS IN THE SUPERSONIC JET SPECTRUM OF MONO-METHYL TETRAZINE

1. C.A. Haynam and D.H. Levy, J. Phys. Chem. 87, 2091 (1983). 2. M.A. Leugers and C.J. Seliskar, J. Mol. Spectrosc. 91, 150-164 (1982). 3. S.M. Beck, M.G. Liverman, D.L. Monts and R.E. Smalley, J. Chem. Phys. 70, 232-237 (1979).Author Institution: Department of Chemistry, University of CincinnatiIdentification of the strong torsional transitions, with $m^{\prime}=m^{\prime\prime}=\pm 1$ and delta m equal to zero, in the high-resolution laser excitation molecular beam spectrum of the methyl tetrazine 5613 {\AA} origin band recently published by Haynam and Levy (1) has been made. Use of their published tetrazine frame rotational constants with $A_{T} = 5.3403 cm^{-1}, \triangle A_{T} = -0.034 cm^{-1}$ results in predicting the positions of the torsional transitions for J up to 3 to within about $.001 cm^{-1}$ precision. However, line positions for larger values of J are not adequately calculated using these constants in the asymmetric top/free internal rotor model (2), the fit worstening with increasing J. Reasons for this discrepancy are discussed. Assumption of an equilibrium distribution over both rotation and torsion states for a specified temperature does not quantitatively reproduce the observed molecular beam spectrum intensities. However, a simple model based on a suggestion of Smalley, et al. (3) does produce the observed spectral intensities in at least the simplest of the Haynam and Levy (1) spectra. Indeed, this simple model, with $T_{rot} = 0.50K$ and $T_{m=1} = 5.0K$ reproduces the published 500 PSI backing-pressure spectrum on a line-for-line basis

ELECTRONIC BAND CONTOUR CALCULATION OF TOLUENE

$^{1}$ E. B. Wilson, JR., C. C. Lin, and D. R. Lide, JR., J. Chem. Phys. 23, 136--142 (1955).Author Institution:The rotational contour of the origin band of toluene has been computed within the framework of the asymmetric top with free internal rotation (1). With the basis |J, Ka, Kc, M, m $>$ and the barrier height equal to zero, the energy matrix becomes diagonal in the torsional quantum number, m, and the secular equation is then factorable into even and odd K sub-blocks. The selection rules for dipole radiation are the same as for the rigid asymmetric top with the additional constraint that $\Delta m =$O. A general program has been written so that the rotational band contour for any molecule in this class may be computed

Error-Prone Polymerase, DNA Polymerase IV, Is Responsible for Transient Hypermutation during Adaptive Mutation in Escherichia coli

The frequencies of nonselected mutations among adaptive Lac(+) revertants of Escherichia coli strains with and without the error-prone DNA polymerase IV (Pol IV) were compared. This frequency was more than sevenfold lower in the Pol IV-defective strain than in the wild-type strain. Thus, the mutations that occur during hypermutation are due to Pol IV