Collision free lifetimes of excited NO2 under very high resolution

Nanosecond time-resolved IR emission from molecules excited in a supersonic jet: Intramolecular dynamics of NO2 near dissociation

IR emission from NO2 cooled in a supersonic jet and excited to a single, B 2B1 state rovibronic level at 22 994.92 cm(-1) above the ground-state zero point was detected with 10(-8)-s time resolution. The IR emission together with the laser-induced fluorescence decay measurement allows the deduction of the relaxation dynamics near the dissociation of NO2. Following the excitation this single rovibronic B 2B1 level decays on 1.0-s time scale primarily through electronic radiation. Collisions induce internal conversion with a rate constant of 3.0 x 10(7) Torr(-1) s(-1) to the mixed AX states. Collisions further induce internal conversion of the AX mixed states into highly vibrationally excited levels in the X states with a rate constant at least one order of magnitude slower. This mechanism results in the observation of a double-exponential decay in the laser-induced fluorescence and a rise in the IR emission intensity corresponding to the fast decay in the fluorescence intensity. The IR emission rate of the highly vibrationally excited X-state levels is estimated to be about one order of magnitude larger than the isoenergetic AX mixed states and much larger than the B 2B1 level, both with much less vibrational excitation.

Precision interferometer calibration technique for wavelength measurements: iodine wavelengths at 633 nm and H(alpha)

We describe a precision interferometer calibration technique useful for the measurement of the wavelength of atomic and molecular transitions with megahertz accuracy. Using this technique, the wavenumber of the ith hyperfine component of the (127)I(2) B-X R(73) 5-5 transition, which falls within the Doppler width of the hydrogen Balmer-alpha line, has been determined to be 15233.367390(42) cm(-1).