Heavy atom nitroxyl radicals. II: Spectroscopic detection of H(2)As=O, the prototypical arsenyl free radical.
The previously unknown arsenyl (H(2)AsO) free radical has been identified in the gas phase through a combination of laser-induced fluorescence and single vibronic level emission spectroscopy in a supersonic expansion. Three isotopologues, H(2)AsO, HDAsO, and D(2)AsO have been detected as products of an electric discharge in mixtures of arsine or deuterated arsines, CO(2), and argon. The observed spectra are assigned as due to the B (2)A(')-X (2)A(') electronic transition in which an electron in the ground state pi orbital is promoted to the pi( *) orbital. Rotational analysis of high-resolution spectra proves that the radical is nonplanar in both electronic states with the following r(0) structures: r(")(As-H)=1.513(4) A, r(")(As-O)=1.672(1) A, theta(")(HAsH)=101.8(4) degrees , ground state out-of-plane angle=63.1 degrees ; r(')(As-H)=1.525(10) A, r(')(As-O)=1.806(3) A, theta(')(HAsH)=93.4(10) degrees , and excited state out-of-plane angle=70.7 degrees . Small hyperfine splittings in the spectra have enabled the determination of the arsenic Fermi contact parameter in both states. The results of our ab initio studies of the ground and excited state of this radical (see immediately preceding paper) are in good agreement with the spectroscopic analysis.
He
Sheng-Gui
SG
Beijing National Laboratory for Molecular Species, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
Sunahori
Fumie X
FX
Yang
Jie
J
Clouthier
Dennis J
DJ
D018360:Crystallography, X-Ray; D004563:Electrochemistry / Q000379:methods*; D004581:Electronics; D004583:Electrons; D005609:Free Radicals / Q000032:analysis* / Q000737:chemistry; D005740:Gases / Q000032:analysis / Q000737:chemistry*; D007287:Inorganic Chemicals / Q000032:analysis*; D007700:Kinetics; D008163:Luminescent Measurements; D008954:Models, Biological; D008956:Models, Chemical; D015394:Molecular Structure; D010777:Photochemistry / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*; D013057:Spectrum Analysis; D013237:Stereoisomerism; D014732:Vibration
D005609:Free Radicals; D005740:Gases; D007287:Inorganic Chemicals