Knowledge Bank

The $\nu 1$ (CO stretch) fundamental band of FeCO, which is a linear radical with the $X3\Sigma$ ground electronic state, was observed by time-resolved infrared diode laser spectroscopy. The FeCO radical was produced by the photolysis of pentacarbonyliron $Fe(CO)s$ with 193 nm ArF excimer laser light. More than 90 absorption lines have been assigned to the $\nu 1$ fundamental band of FeCO including the $F1,F2$ and $F3$ spin components in the 1935-70 cm region. Several lines, observed as doublet due to the t-type splitting, were assigned to the hot band from the $\nu 2(bend\sim 330cm-1)$ state. The lifetime of FeCO was about 0.5 msec in the present condition. The rotational and spin-spin interaction constants of the ground state. $BO=4364.92(13)MHz,D0=2.481(41)kHz$, and $\lambda 0=532.49(91)GHz$, as well as those for the $\nu 1$ state are derived from the diode laser spectrum combined with the rotational spectrum in the $F1$ substate of the ground state by FTMW spectroscopy (1). The vibrational band origin obtained $1946.46943(35)cm-1$ is consistent with the value by the photoelectron spectroscopy of the FeCO negative ion. $1950\pm 10cm-1$ (2). A number of spectral lines were observed in the region of $1935-60cm-1$ which are likely due to the degenerate CO stretch band of the $Fe(CO)3$ species.