OH(A 2Σ+) and rare gas-deuteride (NeD, ArD) excimers generated in microcavity plasmas:: Ultraviolet emission spectra and formation kinetics

Emission in the ultraviolet from the A (2)Sigma(+) electronic excited states of OH, NeD, and ArD, and the formation kinetics of these excited heteronuclear diatomics, have been investigated in microcavity plasmas generated in rare gas/H2O or D-2 gas mixtures. Excitation transfer from the a (3)Sigma(+)(u)(1(u),0(u)(-)) Rydberg state of Ar-2 appears to be the dominant pathway to OH(A (2)Sigma(+)) formation in Ar/H2O vapor mixtures with total pressures of 400-800 Torr and H2O partial pressures of 100 mTorr-3 Torr. Maximum emission on the (v('),v('))=(0,0) vibrational band of the OH(A -> X) transition is observed in a 25 mu m, 45 nl microcavity for 600-800 Torr Ar/0.5 Torr H2O mixtures. Comparisons of experimental and simulated fluorescence spectra show the OH[A (2)Sigma(+)(v(')=0)] state rotational temperature to be 425 K for 600 Torr Ar/100 mTorr H2O mixtures but to rise linearly with the H2O partial pressure and exhibit a slope of 170 K/Torr H2O for 100 mTorr <= p(H2)O <= 3 Torr. Excitation of Ne or Ar/D-2 gas mixtures in 50x50 arrays of Si microplasma devices generates broadband spectra, peaking in the mid-ultraviolet (lambda similar to 280-320 nm), which are attributed to the A -> X transition of the ArD or NeD excimers. The optimal D-2 concentration is observed to be similar to 0.5% and the primary kinetic formation mechanism for the deuterides involves D atom transfer in collisions between Ar(4s P-3) and D-2. (C) 2007 American Institute of Physics.