Quenching of excited P-1(1) state atomic zinc by molecular nitrogen: A matrix-isolation spectroscopy/quantum chemical calculation study

A concentration study is used to identify the optical absorption of zinc at oms isolated in solid nitrogen. Photoexcitation of the threefold-split, ato mic 4p P-1(1) singlet absorption band did not produce any emission from eit her the singlet or triplet states. Hartree-Fock (relativistic effective cor e potentials) plus variational and multireference perturbational configurat ion-interaction calculations are performed to analyze this very efficient q uenching of excited state atomic zinc by molecular nitrogen. Of the two geo metries considered in energy calculations of the approach of Zn(P-1(1)) to N-2, the collinear exhibited a slightly greater stabilization than the perp endicular approach. However, the collinear is identified as of no significa nce in the excited state quenching due to the absence of low energy crossin gs with the ground state. In contrast, for the perpendicular approach a cro ssing between the repulsive ground (1)A(1)(S-1(0)) state and the strongly a ttractive B-1(2)(P-1(1)) state occurs close to the energy minimum of the B- 1(2) state. The efficiency of crossing between these states is analyzed in the framework of one-dimensional Landau-Zener (LZ) theory. A hopping probab ility of 0.07 is obtained for a single crossing, considered important in a rapidly relaxing solid state system, such as present in a low temperature m atrix. Crossings found between the repulsive B-3(1)(P-3(1)) and (3)A(1)(P-3 (1)) states with the strongly bound B-1(2)(P-1(1)) state are expected to pl ay a role in gas phase Zn(P-1(1)) quenching leading to the production of Zn (P-3(J)) states. LZ calculations indicate a small hopping probability for t hese crossings, consistent with the small P-1(1)--> P-3(J) quenching cross sections observed in the gas phase work. (C) 2001 American Institute of Phy sics.