Knowledge Bank

A laser Stark spectrometer has been used to record the spectrum of the $\nu 4$-band of $POF3$ with the R(38) to R(52) laser lines of the 10.4 $\mu m$ band of $CO2$. The sample cell consists of a 6-inch Pyrex tee which contains a pair of polished nickel plates separated by six precision-ground quartz spacers (nominal thickness, 1 mm). An electric field up to 60 kv/cm can be applied at a sample pressure of 5 mTorr, A 10 kHz sinusoidal modulation was applied to one of the plates. The signal detected by a Pb-Sn-Te photovoltaic detector was amplified, phase-sensitively detected, and displayed on an oscilloscope or a chart recorder. The $POF3$ molecule, which is accidentally very close to a spherical top, has a small rotational constant $(Bo=4,6$ GHz) for ordinary infrared spectroscopy. No high-resolution infrared study has been reported. The Stark spectrum appeared extremely complicated with many overlapping lines. More than sixty transitions were assigned, although a great number of lines remain unassigned. The electric dipole moments in both the ground and excited states were determined precisely along with other molecular constants.