Spectroscopy and dynamics of jet-cooled hydrazines and ammonia. II. Electron-impact dissociative ionization

Journal Article · Sun Nov 01 04:00:00 EST 1992 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.463719· OSTI ID:6898262

Syage, J A ^[1]

---

1. The Aerospace Corporation, P. O. Box 92957/M5-754, Los Angeles, California 90009 (United States)

Dissociative-ionization cross sections, fragment appearance potentials, and fragment kinetic energies were measured for electron-impact excitation of jet-cooled NH[sub 3], hydrazine (N[sub 2]H[sub 4]), and monomethyl hydrazine (MMH) over an energy range of 10--270 eV. A data base of 35 parent and fragment ions is reported. All measurements were made in a crossed electron--molecular beam apparatus using pulsed extraction and time-of-flight mass detection to ensure field-free excitation and high collection efficiency for energetic ions. Cross sections for NH[sub 3] ionization are in good agreement with previous measurements except for ions with high kinetic energy (KE). These discrepancies are attributed to instrument-dependent KE detection efficiencies in the previous results. Cross section data have not been previously reported for N[sub 2]H[sub 4] and MMH. The measured cross sections for total ionization at 70 eV are 2.35 A[sup 2] (NH[sub 3]), 3.76 A[sup 2] (N[sub 2]H[sub 4]), and 4.20 A[sup 2] (MMH). KE distributions were measured by an ion deflection method and gave results consistent with time-of-flight peak-shape analysis. Mean KE values [lt][epsilon] [ital t][gt] are reported for all fragment ions studied. For 170-eV excitation of NH[sub 3], [lt][epsilon] [ital t][gt] varied from 0.026 eV (NH[sub 2][sup +]) to 1.4 eV (H[sup +]). The kinetic energies for N[sub 2]H[sub 4] and MMH fragment ions at similar excitation energies are typically much lower than for fragment ions from NH[sub 3], conforming to statistical arguments based on density of internal states. High resolution mass spectra were recorded for MMH in order to distinguish different fragment ions of the same unit mass.

• OSTI ID: 6898262
• Journal Information: Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 97:9; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

664300* -- Atomic & Molecular Physics-- Collision Phenomena-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
ALKYL RADICALS
AMMONIA
BEAMS
COLLIDING BEAMS
COLLISIONS
COOLING
CROSS SECTIONS
DISSOCIATION
ELECTRON COLLISIONS
ELECTRON-MOLECULE COLLISIONS
ENERGY
ENERGY RANGE
EV RANGE
EV RANGE 10-100
EV RANGE 100-1000
HYDRAZINE
HYDRIDES
HYDROGEN COMPOUNDS
IONIZATION
JETS
KINETIC ENERGY
MASS SPECTROSCOPY
METHYL RADICALS
MOLECULE COLLISIONS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
PULSES
RADICALS
RESOLUTION
SPECTROSCOPY
TIME-OF-FLIGHT METHOD