Konstanz 1998 – wissenschaftliches Programm

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MO: Molekülphysik

MO 5: Photodissoziation I

MO 5.2: Vortrag

Dienstag, 17. März 1998, 14:15–14:30, M629

Double Resonance Overtone Photofragment Spectroscopy of trans-HONO — •Rainer Beck¹, Thomas R. Rizzo¹, Florian Reiche², and Bernd Abel² — ¹Laboratoire Chimie Physique Moleculaire, EPFL-Lausanne, Switzerland — ²Institut f"ur Physikalische Chemie, Universit"at G"ottingen, Germany

Double resonance overtone photofragment spectroscopy (DROPS) has been used to study the previously unobserved v_OH = 5,6, and 7 overtones of gas phase trans-nitrous acid in its electronic ground state. Double resonance excitation via individual rovibrational states of v_OH =1 or 2 is used to selectively populate single ro- vibrational states belonging to the v_OH = 5, 6, or 7 overtones of the O-H local mode vibration. Absorption into quasibound states above the dissociation limit is detected through laser induced fluoresence of the OH fragment. Observing dissociation from different rovibrational states of the v_OH = 5 band near thre- shold determines precisely the HO-NO bond energy to be D₀ 16784.6 +- 1.9 cm⁻¹. We also report band orgins and spectroscopic constants as well as homogeneous linewidths for v_OH = 5,6, and 7 of trans-HONO. The results of the study on HONO demonstrate that DROPS is a powerful technique to study vibrational overtone transitions and to measure precise bond energies of molecules even if these are only minority species in a mixture.