Millimeter-wave spectroscopy, high resolution infrared spectrum, ab initiocalculations, and molecular geometry of FPO

The transient FPO molecule was produced in a flow by pyrolysis of 5% F2POPF 2 in Ar at 1300-1400 degreesC. High resolution (0.008 cm(-1)) Fourier trans form infrared spectra of the a-type v(1) and v(2) bands centered at 1297.54 and 819.57 cm(-1), respectively, were measured and fitted to excited state parameters up to quartic centrifugal distortion constants. Millimeter-wave spectra between 300 and 370 GHz of FPO in the ground and excited states we re recorded, and 124 and 86 lines, respectively, including for both states a- and b-type transitions, were measured and fitted to a Watson A-type Hami ltonian up to sextic centrifugal distortion terms. High-level ab initio cal culations with large basis sets were performed for FPO to provide reliable structural parameters as well as harmonic [CCSD(T)/AVQZ+1] and anharmonic [ MP2/VQZ+1] force fields up to quartic terms. The spectroscopic constants de rived from these force fields are generally in excellent agreement with exp eriment. The calculations moreover suggest anharmonic interactions between and and between v(1) and v(2) + v(3). Deperturbation of the v(1) = 1 and v( 2) = 1 levels was done, and the results are in support of a band center of v(3) close to 412 cm(-1). Consistent experimental and theoretical equilibri um structures were determined for FPO, with r(e)(PO) 145.3 pm, r(e)(PF) 157 .3 pm and theta (e)(FPO) 110.1 degrees. The collision-controlled 1/e life-t ime of FPO generated by an electric discharge in an F2POPF2/Ar mixture at 8 -10 Pa and at room temperature is 8 ms.