Observation of CrCO in the 5 μm multiphoton decomposition of Cr(CO)6

Chromium monocarbonyl CrCO has been observed in the 5 μm infrared multiphoton decomposition of gas-phase Cr(CO)6 using the time-resolved single-photon dissociation technique. The weak CrCO binding of less than 1.5 kcal mol−1 has been clarified. The products of the IR MPD were monitored with a UV laser in the range 315–354 nm. Fluorescence of Cr atoms at ∼ 359 (y7PJ0 → a7S3) and ∼ 427 nm (z7PJ0 → a7S3) was detected all over the range and its intensity was proportional to the UV fluence, implying that single UV photon absorption of transient species gave the atomic fluorescence and that its binding energy is small. The transient was decomposed by collisions with Ar with a rate constant of (9.2 ± 0.6) × 10−12 cm3 s−1, which was close to the collisional formation rate constant of the ground-state Cr atoms. All the experimental results are consistent with the assignment of the transient species to CrCO.