Collisional energy transfer in the multiphoton decomposition of tert-butyl methyl ether

The multiphoton decomposition of tert-butyl methyl ether (TBME), (CH{sub 3}){sub 3}COCH{sub 3}, has been investigated for the purpose of laser isotope separation (LIS) of oxygen isotopes. The multiphoton decomposition (MPD) of tert-butyl methyl ether (TBME) was studied with a 100-ns pulsed CO{sub 2} laser operating on the 9R(20) line and at a fluence of 12 J/cm{sup 2}. For TBME pressures up to 2.7 kPa, MPD gave the following products: 2-methylpropene (TMP), methanol, 2-methyl-2-butene, acetone, methane, hydrogen, ethane, and ethane. The products result from reactions among the species produced through two channels: (1) TMP + methanol; (2) acetone + 2CH{sub 3}. A collision-dependent reaction scheme is presented to explain the pressure dependence of the MPD. In this instance, significant energy transfer between two laser-excited TBME molecules occurs before decomposition takes place. The decomposition products deactivate excited TBME molecules and reduce subsequent decomposition.