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

Journal Article · Thu Oct 17 00:00:00 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), Vol. 95:21; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

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