No abstract

No abstract

The N–O degenerate stretching band ν3 of the NO3 radical has been studied in the gas phase by infrared tunable diode laser spectroscopy. The NO3 radical was generated by the reaction of NO2 with an excess of O3. Zeeman modulation was employed to observe the paramagnetic absorption lines of 14NO3 and 15NO3 in the wavelength regions 1480–1500 and 1463–1479 cm−1, respectively. Only K′′=3n (n denoting an integer) transitions were observed, and the N′′=even members were missing from the K′′=0 manifold. These observations indicate that the NO3 radical belongs to D3h symmetry in the 2A2′ ground electronic state. The observed spectrum was analyzed using a symmetric-top vibration-rotation Hamiltonian including the spin-rotation interaction. The main parameters thus obtained for 14NO3 are B3=0.455 22(11), C3=0.227 13(6), Cζ3=0.044 79(11), q3=0.001 624(33), t3= 0.000 000 458 0(43), B0=0.457 46(12), C0=B0/2 (fixed), εbb=0.0280(27), and εcc=0.1197(36) for v3=1, εbb=0.0277(28), and εcc=0.1117(34) for v=0, and ν0=1492.3929(9), all in cm−1 with one standard error in parentheses. Although these parameters well reproduced the observed spectrum, the following anomalous features were noted: (1) a large εcc spin-rotation interaction constant was required to explain the spin splittings for both the ν3 and ground states, (2) a higher-order vibration-rotation interaction term having Δk=±4 and Δl=±2 needed to be included, with the corresponding interaction constant t3 larger than that of CHF3, and (3) the centrifugal distortion constants and the first order Coriolis coupling constant which were derived did not agree with those calculated assuming a reasonable force field. These anomalies were ascribed to the interaction with a low-lying excited electronic state and, to some extent, with a combination or overtone state. The N–O bond length was calculated from the B0 rotational constant to be 1.240 Å, in good agreement with an ab initio calculated value.

Ishiwata et al. [J. Chem. Phys. 82, 2196(1985] have recently observed an infrared diode laser spectrum of N0 3 in the 1492 cm -I region and have assigned it to the V3 band in the X 2 A i state. However, some of the derived constants such as the Coriolis coupling and spin-rotation constants did not conform well with expected values. In the present study, the observation was extended so as to take combination differences, which led us to revise the previous assignment slightly and to remove all the anomalies in the lower (i.e., ground) state. A most important result of the present study is that a spin-orbit interaction constant a eff I (L z ) I = 0.17 cm -I is indispensable to explain the spin splitting observed for the upper state. The first-order Coriolis coupling constant of the upper state (; = 0.19) remains essentially the same as in the previous study and differs considerably from the value calculated for the V3 state (; = 0.7). Possible explanations of these data are discussed in some detail to obtain more information on the molecular structure of the N0 3 radical.

t-Bu),BzN(O)nitrobenzyl bromide, 100-11-8; p-nitrobenzyl duryl nitrodide, 84802-29-9; methyl iodide, 74-88-4; N-methyl-N-tris(tert-bu-ty1)phenyl nitroxide radical, 33721-34-5; N-methoxy-N-tris-(tert-buty1)phenyl anilino radical, 64191-72-6; benzyl bromide, electrochemical cell. CHZ(CBHJNO2,,BzN(O)H,The nitrate radical, NO3, was directly detected by the laser-induced fluorescence method. The band structure of the fluorescence excitation spectrum was consistent with that of the absorption spectrum. The fluorescence spectrum excited at 662 nm corresponding to the 0-0 transition showed progressions with 1060-and 1480-cm-' intervals, which were assigned to the symmetric stretching (vl) and degenerate antisymmetric stretching (v3) modes of the ground state NO,, respectively. The fluorescence lifetime excited at the 0-0 band was estimated to be 2.8 ~s from the Stern-Volmer plots in the pressure region of 0.04-0.6 torr.(9) J. R. McDonald, private communication. Geophys. Res. Lett., 7 , 89 (1980).Perturbations around steady states of a system of cerium or manganese bromide and bromate ions in a sulfuric acid solution, in a continuous stirred tank reactor (CSTR), are investigated. Two kinds of perturbations are discussed, namely, small-species and large-constraint ones. The feasibility of measuring a particular rate constant by following the system behavior after a small perturbation is analyzed. Some general theorems regarding this behavior are obtained. Large perturbations, namely, those that cause a transition of the system from one steady state to another, are analyzed and an approximate relationship between the perturbations' intensity and length is developed. The results are in good agreement with the experimental data.