Crossed-molecular beam apparatus time-of-flight computer interface

A variety of gas phase reactions of barium and tin atoms were studied using a crossed molecular beams machine with a universal quadrupole mass filter based detection system incorporating a time-of-flight (TOF) spectrometer for velocity analysis. Center-of-mass (CM) reactive product recoil angle and relative recoil energy distributions were measured for the following reactions: (1) Ba + N2O--BaO + N2, (2) Ba + CO2--BaO + CO, (3) Ba + O2--BaO + O, (4) Sn + Cl2--SnCl + Cl, (5) Sn + CH3I--SnI + CH3, (6) Sn + n-C3H7I--SnI + C3H7I, and (7) Sn + CCl4--SnCl + CCl3. At relative collision energies below 15kJmole-1, the BaO product of reaction (1) is seen to be sharply backwards scattered with only 10 to 20 percent of the total available energy in product recoil energy. These results are consistent with near 100 percent efficiency for production of electronically excited BaO. Evidence of a significant effect of N2O vibrational energy on the total reactive cross section is presented. Reaction (2), at collision energies as high as 31kJmole-1, and reaction (3), at a collision energy of 13kJmole-1, both seem to proceed via a long-lived complex, and their product recoil energy distributions are reasonably well fit by the transition state theory of Herschbach et al. No evidence of a CO2 internal energy effect on the total reactive cross section for reaction (2) was found. The SnCl product of reaction (4) was predominately forward scattered with low product recoil energy; the SnI product of reactions (5) and (6) were sharply backwards scattered with relatively high recoil energies; the SnCl product of reaction (7) was sideways scattered. Thus the reactions of tin atoms studied here are very similar to the corresponding alkali and alkaline earth metal atom reactions. A minicomputer interface for collection and display of TOF spectrums and product angular distributions was built using a Digital Equipment Corp. PDP8/e computer and is described here in detail