The diatomic dication CuZn$^{2+}$ in the gas phase

R. PIS DIEZ; K. FRANZREB; J.A. ALONSO

JOURNAL OF CHEMICAL PHYSICS

AMER INST PHYSICS

Año: 2011 vol. 135 p. 1 - 5

0021-9606

In the present combined experimental and theoretical study we report the observation of the novelgas-phase dication CuZn2+ and provide some theoretical insight into the electronic binding of thisexotic metastable molecule and its formation mechanism. Using mass spectrometry we have detectedfour isotopomer signals of CuZn2+ at half-integer m/z values for ion flight times of about14 μs. CuZn2+ was unambiguously identified by its isotopic abundance. High-current energetic Ar+ion bombardment of a brass surface was used for its production. Subsequent dication formation wasfound to take place in the ion extraction region of our mass spectrometer several tens of micronsin front of the sputtered brass surface. The dication formation mechanism appears to be resonantelectron transfer in soft gas-phase collisions between sputter-ejected singly charged CuZn+ molecularions and incoming Ar+ projectiles. This conclusion is supported by our theoretical study thatobtained an ionization energy of CuZn+ of 15.75 eV, in excellent agreement with both the experimentaland calculated ionization energy of Ar (15.76 and 15.67 eV, respectively). The ground state ofCuZn2+ is found to be a metastable one with a very shallow potential well at an internuclear equilibriumdistance of about 2.7 Å, the dissociation energy being very difficult to estimate. Interestingly,spin-orbit corrections are found to be necessary to get an adequate description of the metastablestate of CuZn2+, whereas relativistic corrections have no effects on neutral CuZn nor on CuZn+.