High resolution study of spin-orbit mixing and the singlet-triplet gap in chlorocarbene: Stimulated emission pumping spectroscopy of (CHCl)-Cl-35 and (CDCl)-Cl-35

摘要

We report on high resolution studies of spin-orbit mixing and the singlet-triplet gap in a prototypical halocarbene, CHCl, using stimulated emission pumping (SEP) spectroscopy from the (A) over tilde 1A'' state. Results are reported for two isotopomers, (CHCl)-Cl-35 and (CDCl)-Cl-35. We have obtained rotationally resolved spectra for the majority of (X) over tilde (1)A' levels lying between 0 and 6000 cm(-1) above the zero-point level that were previously observed under low resolution in single vibronic level emission studies and several new levels that were previously unobserved or unresolved. In addition, SEP spectra were obtained for six (a) over tilde (3)A'' levels in (CHCl)-Cl-35 and three levels in (CDCl)-Cl-35. The derived term energies and rovibrational parameters of the (X) over tilde (1)A' and (a) over tilde (3)A'' states are in good agreement with theory. The (a) over tilde (3)A'' triplet spin-spin parameter is vibrational state dependent, and dominated by a second-order contribution from spin-orbit coupling with nearby (X) over tilde (1)A' levels; it therefore provides a sensitive probe of spin-orbit mixing in this system. An analysis of three pairs of interactions between specific (a) over tilde (3)A'' and (X) over tilde (1)A' levels in (CHCl)-Cl-35 affords a pure electronic spin-orbit coupling element of 150 cm(-1), in good agreement with theoretical expectations. The derived singlet-triplet gaps, which are the most precise determined to date for any carbene, are compared with the predictions of high level ab initio theory. (c) 2008 American Institute of Physics.