The First Observation of a Gaseous Triatomic Containing a Transition Metal Atom: The Visible Spectrum of HYN

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Ohio State University

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Supersonic expansion of a $NH_{3},/He$ gas mixture through a laser-produced plasma of yttrium atoms has yioldod the formation of the HYN molecule which was studied by laser-induced-fluorescence. The carrier was confirmed by isotopic substitutions yielding HY14N, DY14N, HY15N and the magnetic hyperfine structure arising from the spinning Y nucleus. In the visible, fluorescence can be excited in only 3 regions centered around 700, 640 and 598 ma, For all the transitions analyzed so far the molecule appears to remain linear. The 700 ma region is characterized by two sub-bands assigned as the (0,0) band of $a ^{2}\Pi -^{2}\Sigma$ transition in which the spin-orbit splitting is about $90 cm^{-1}$. The 640 nm region is characterized by at least one strong band showing the features of a $^{2}\Pi -^{2}\Sigma$ transition. The 598 ma region is characterized by several bands among which the strongest is assigned as the (0,0) band of a $^{2}\Sigma -^{2}\Sigma$ transition. All the transitions examined so far appear to terminate as the same lower $^{2}\Sigma$ state that we assign as the ground state of HYN. The spectrum of the $^{2}\Sigma -^{2}\Sigma (0,0)$ band has been recorded at high resolution (120 MHz) and has yielded accurate spectroscopic constants which will be discussed. The spectrum is characterized by beautiful nuclear magnetie hyperfine structure which is due solely to the Y nucleus and which is attributable exclusively to the ground state. The coupling case follows a gradual transition from $b_{\beta S}$ to $b_{\beta H}$. High resolution studies on the other systems are currently underway and detailed analysis will be available at the time of the meeting.


Author Institution: Laser Chemistry Group, National Research Council of Canada; Department of Chemistry, University of Victoria; Institute of Laser Engineering, Osaka University; Laser Chemistry Group, National Research Council of Canada