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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 25, Number 2
BKCSDE 25(2)
February 20, 2004 

Reaction of Cr Atoms with O2 at Low Pressures: Observation of New Chemiluminescence Bands from CrO2
Hyung Su Son, Ja Kang Ku*
Cr atoms, Chemiluminescence, CrO2*
Ground and low-lying electronic states of Cr atoms in the gas phase were generated from photolysis of Cr(CO)6 vapor in He or Ar using an unfocussed weak UV laser pulse and their reactions with O2 and N2O were studied. When 0.5-1.0 Torr of Cr(CO)6 /O2 /He or Ar mixtures were photolyzed using 295-300 nm laser pulses, broadband chemiluminescence peaked at ~420 and ~500 nm, respectively, was observed in addition to the atomic emissions from z7Po, z5Po, and y7Po states of Cr atoms. When N2O was used instead of O2, no chemiluminescence was observed. The chemiluminescence intensities as well as the LIF intensities for those three low-lying electronic states (a7S3, a5S2 and a5DJ) showed second-order dependence on the photolysis laser power. Also, the chemiluminescence intensities were first-order in O2 pressure, but the presence of excess Ar showed a strong inhibition effect on them. Based on the experimental results, the chemiluminecent species in this work is attributed to CrO2* generated from hot ground state Cr atoms with O2. The apparent radiative lifetimes of the chemiluminescent species and collisional quenching rate constants by O2 and Ar also were investigated.
226 - 232
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