Abstract
Negative ion-molecule reaction has been investigated for formic acid utilizing a conventional type mass spectrometer. At elevated pressure negative ions react with neutral species in the ion source of mass spectrometer. It was found that a negative ion of mass 91 is produced by the reaction of the HCOO- ion with neutral formic acid as
HCOO-+HCOOH→HCOOHCOOH-
This reaction has two processes, i.e. a dissociative resonance electron capture (DREC) process and a high energy electron process. From the studies of HCOOH gas pressure dependence it was observed that the intensities of the HCOO- and HCOOHCOOH- ions in a DREC process increase with first and second order of the HCOOH gas pressure, whereas in a high energy electron process, they increase with fourth and seventh order of the pressure, respectively. The reaction rate constants of two processes were determined as (6.8 ±1.5) ×10-13 cc/molecule.sec for a DREC process and (1.3 ±0.5) ×10-37 cc3/molecule3·sec for a high energy electron process.
