Evaporative dissociation of ammonia cluster ions: Quantification of decay fractions and isotope effects

Journal Article · Thu Oct 17 04:00:00 EDT 1991 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100174a053· OSTI ID:7265872

Wei, S; Kilgore, K; Tzeng, W B; Castleman, Jr, A W ^[1]

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1. Pennsylvania State Univ., University Park (United States)

A modified version of the evaporative ensemble model is employed to deduce relative binding energies for protonated cluster ions using previously measured metastable dissociation fractions of ammonia cluster ions, (NH{sub 3}){sub n}H{sup +}, n = 4-22, obtained by using a laser-based time-of-flight mass spectrometer equipped with a reflection. The newly derived values are found to be in good agreement with those reported earlier based on high-pressure mass spectrometry (HPMS) and several other methods employing data on dissociation dynamics. The various methods are found to be complementary. New measurements are reported for the metastable decay of deuterated cluster ions to investigate the influence of mass effects on the dissociation rate. The decay fractions of the cluster ions (ND{sub 3}){sub n}D{sup +} are found to be consistently higher than those of the corresponding (NH{sub 3}){sub n}H{sup +} by 15%. The isotope effect can be well accounted for by considering the differences of their bulk heat capacities, and such studies are found to be a promising method for measuring the heat capacities of small, unsupported cluster systems.

• DOE Contract Number: FG02-88ER60648
• OSTI ID: 7265872
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 95:21; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
BINDING ENERGY
CATIONS
CHARGED PARTICLES
DATA
DEUTERIUM COMPOUNDS
DISSOCIATION
DYNAMIC MASS SPECTROMETERS
DYNAMICS
ENERGY
ENERGY LEVELS
EVAPORATION
EXCITED STATES
EXPERIMENTAL DATA
HYDROGEN COMPOUNDS
INFORMATION
IONIZATION
IONS
ISOTOPE EFFECTS
MASS SPECTROMETERS
MASS SPECTROSCOPY
MATHEMATICAL MODELS
MEASURING INSTRUMENTS
MECHANICS
METASTABLE STATES
NITROGEN COMPOUNDS
NUMERICAL DATA
PHASE TRANSFORMATIONS
PHOTOIONIZATION
PHYSICAL PROPERTIES
SPECIFIC HEAT
SPECTROMETERS
SPECTROSCOPY
THERMODYNAMIC PROPERTIES
TIME-OF-FLIGHT MASS SPECTROMETERS
TIME-OF-FLIGHT SPECTROMETERS