Laboratory Rotational Spectrum of PH (N = 2 ← 1) in the 1 THz Region

Abstract

Abstract The N = 2 ← 1 rotational transition of the PH radical in its ground electronic (X3 Σ- ) and vibrational states has been measured with the Cologne terahertz spectrometer in the frequency region between 920 and 1070 GHz. The PH radical was generated by immersing red phosphorus in a dc glow discharge of molecular hydrogen buffered with argon. Transition frequencies of the five J′ - J″ fine structure components together with the associated hyperfine structure patterns were precisely measured and analyzed to derive highly accurate molecular parameters, which are more extensive than those reported in the existing literature. Among the determined parameters are the rotational constant B0 = 252200.8099(63) MHz and the centrifugal distortion constant D0 = 13.2915(33) MHz, as well as two fine structure constants - the spin-rotation constant γ0 and the spin-spin interaction constant λ0 - together with their centrifugal distortion contributions Dγ0 and Dλ0. Furthermore, each of the magnetic hyperfine parameters bF, c, and the nuclear spin-rotation constants CI were obtained for both nuclei. The accuracy of previously obtained molecular constants has been improved by up to one order of magnitude. This new set of molecular parameters allows highly reliable frequency predictions of the rotational spectrum extending into the far infrared region; such transition frequencies may be of interest for interstellar spectroscopy.