| Abstrakt: |
The millimeter/submillimeter spectrum of magnesium chloride (MgCl) has been observed in two new electronic excited states, (3)2Σ+and (4)2Σ+, using direct absorption methods. The molecule was synthesized in a mixture of Cl2, argon, and magnesium vapor. For the (3)2Σ+state, multiple rotational transitions were measured in the v= 0 level for all six isotopologues (24Mg35Cl, 24Mg37Cl, 25Mg35Cl, 25Mg37Cl, 26Mg35Cl, and 26Mg37Cl), as well as up to v= 13 for 24Mg35Cl. For the (4)2Σ+state, less intense spectra were recorded for 24Mg35Cl (v= 0–2). Equilibrium rotational parameters were determined for both states for 24Mg35Cl, as well as rotational constants and 25Mg hyperfine parameters for the other isotopologues. A perturbation was observed between rotational levels of the two states due to an avoided crossing. Computations were also carried out at the CASPT2 and MRCISD+Q levels, and the resulting bond lengths for (3)2Σ+and (4)2Σ+states agree well with the experimental values of re= 2.536 and 2.361 Å. The computations show that the (3)2Σ+state has a double-well potential; however, the state behaves as a single well with unperturbed vibrational levels up to v= 13 due to nonadiabatic interactions with the (4)2Σ+state. |
