Hyperfine structure in the à state of PH2 arising from the fermi interaction of 31P

Observation of a new phosphorus-containing reactive intermediate: Electronic spectroscopy and excited-state dynamics of the HPBr free radical

The A (2)A(')-X (2)A(") electronic spectra of jet-cooled HPBr and DPBr have been obtained for the first time using the pulsed electric discharge technique with a precursor mixture of PBr(3) and H(2)/D(2). Laser-induced fluorescence and single vibronic level emission spectra gave the bending and P-Br stretching frequencies in the ground and excited states of both isotopomers. Rotational analyses of the HPBr and DPBr 0(0) (0) bands showed small spin splittings characteristic of a doublet-doublet transition of an asymmetric-top molecule. From the ground- and excited-state rotational constants, effective (r(0)) structures were derived with r(")(PH)=1.4307(86) A, r(")(PBr)=2.2021(9) A, and theta(")=95.2(8) degrees, and r(')(PH)=1.434(31) A, r(')(PBr)=2.1669(26) A, and theta(')=115.5(16) degrees . In a few favorable cases, further hyperfine splitting of the spin-rotation energy levels has been observed, due to the excited-state Fermi contact interaction of the unpaired electron with the spin magnetic moment of the (31)P nucleus, with a(F) (')=0.064(9) cm(-1) for HPBr. Fluorescence depletion spectroscopy and lifetime measurements indicate that higher vibrational levels of the A (2)A(') state are predissociated by a X (2)A(") dissociative continuum. CCSD(T)/aug-cc-pVTZ calculations predict that the most likely dissociation process is HPBr (X (2)A("))-->PH((3)Sigma(-))+Br((2)P(u)).

Phosphorus hyperfine structure in the electronic spectrum of the HPCl free radical

The 444 nm 2 0 (1) bands of the A 2A'-X 2A" transition of the jet-cooled HP 35Cl and HP 37Cl radicals have been studied at high resolution using the pulsed electric discharge technique with a precursor mixture of PCl3 and H2. Spectra recorded with linewidths of approximately 360 MHz revealed resolved hyperfine structure in both isotopomers arising from the excited state Fermi contact interaction of the unpaired electron with the magnetic moment of the 31P nucleus, with aF'=0.0641(10) cm(-1) and 0.0636(31) cm(-1) for HP 35Cl and HP 37Cl, respectively. No contribution from the ground state, or excited state contributions from the hydrogen or chlorine nuclei were resolved, confirming ab initio predictions that HPCl is a p pi radical in the X state, and an s sigma radical with a substantial contribution from the phosphorus 3s atomic orbital in the A state. The free atom comparison method has been used to estimate that the singly occupied molecular orbital in the excited state has 14% phosphorus 3s character.

Microwave Spectrum of the PD2 Radical in the 2B1 Ground Electronic State

The rotational spectrum of the PD2 radical in the 2B1 ground electronic state was observed in the region 165-463 GHz using a source-modulated microwave spectrometer. The PD2 radical was generated in a free-space absorption cell by a dc glow discharge of D2 over red phosphorus grains which were placed in the middle of the Pyrex glass cell. One hundred thirty fine and hyperfine components of 20 b-type rotational transitions were measured and analyzed by least-squares methods. The rotational and centrifugal distortion constants, the spin-rotation coupling constants with their centrifugal distortion terms, and the hyperfine coupling constants of both the phosphorus and the deuterium nuclei were precisely determined. The phosphorus nuclear spin-rotation coupling constants were found to have relatively large values: Caa(P) = 0.4815(89) MHz, Cbb(P) = 0.2501 (104) MHz, and Ccc(P) = 0.0564 (74) MHz, as suggested from those of PH2. The harmonic force field of PH2 was derived from centrifugal distortion constants, inertial defects, and the reported vibrational frequencies for PH2 and PD2. The determined force field was used to make harmonic corrections to the observed moments of inertia, and the rz structures for both species were derived,PH2: rz(PH) = 1.43365(23) A, thetaz(HPH) = 91.622(32)degreesandPD2: rz(PD) = 1.42852(17) A, thetaz(DPD) = 91.646(23)degrees,where errors in parentheses are due to residual inertial defects of the corrected moments of inertia. Copyright 1998 Academic Press. Copyright 1998Academic Press