# ROTATIONALLY RESOLVED PHOTOELECTRON SPECTROSCOPY STUDY OF THE FIRST ELECTRONIC STATES OF $Ar^{+}_{2}$

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 Title: ROTATIONALLY RESOLVED PHOTOELECTRON SPECTROSCOPY STUDY OF THE FIRST ELECTRONIC STATES OF $Ar^{+}_{2}$ Creators: Rupper, Patrick; Merkt, F. Issue Date: 2002 Publisher: Ohio State University Abstract: The $I(1/2u)$, $I(3/2g)$, $I(1/2g)$, $I(3/2u)$ and II(1/2u) states of $Ar^{+}_{2}$ have been investigated in the region between $124650 cm^{-1}$ and $128150 cm^{-1}$ by pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectroscopy following $(1 + 1')$ resonance-enhanced two-photon excitation via the $0^{+}_{u}$ Rydberg state located below the $Ar^{\ast} ([3p]^{5}4s'[1/2]_{1}) + Ar (^{1}S_{0})$ dissociation limit of $Ar^{+}_{2}$. By selecting single rotational levels of the intermediate state, the rotational structure of four of the six lowest ionic states of $Ar^{+}_{2}$ could be observed and unambiguous assignments of electronic symmetry of the ionic states could be made on the basis of photoionization selection rules. The rotational structure also provided information on the equilibrium internuclear distances $R^{+}_{e}$ for the $I(1/2u), I(3/2g), I(1/2g)$ and II(1/2u) states $(R^{+}_{e}(I(1/2u)) = (2.393 \pm 0.043) {\AA}, R^{+}_{e} (I(3/2g)) = (2.993 \pm 0.005) {\AA}, R^{+}_{e} (I(1/2g)) = (3.151 \pm 0.002){\AA}$ and $R^{+}_{e} (II(1/2u)) = (3.851 \pm 0.012) {\AA}$). The adiabatic ionization potentials are determined to be $IP(I(3/2g)) = (125685.3 \pm 0.7) cm^{-1}, IP(I(1/2g)) = (126884.1 \pm 0.7) cm^{-1}, IP(I(3/2u)) = (127044.6 \pm 1.5) cm^{-1}$ and $IP(II(1/2u)) = (128000.8 \pm 0.7) cm^{-1}$, from which dissociation energies are obtained as $D^{+}_{0} (I(3/2g)) = (1509.3 \pm 1.2) cm^{-1}, D^{+}_{0}(I(1/2g)) = (310.5 \pm 1.2) cm^{-1}, D^{+}_{0}(I(3/2u)) = (150.0 \pm 1.8) cm^{-1}$ and $D^{+}_{0}(II(1/2u)) = (625.4 \pm 1.2) cm^{-1}$. The interaction between the I(1/2g) and I(3/2g) states could also be observed and analyzed. Description: Author Institution: Physical Chemistry Laboratory URI: http://hdl.handle.net/1811/20479 Other Identifiers: 2002-RE-06