Pulsed Mass Spectrometer Research Articles

Kinetics, equilibria and diffusion of ions produced in N2, CO and CO2, studied as a function of temperature using a high-pressure pulsed mass spectrometer source

Gas phase ion–molecule association reactions of the type A++ A [graphic omitted] A˙ A+ have been studied as a function of temperature in a pulsed electron beam high-pressure mass spectrometer source. Unlike previous studies of this type, the effect of ionic diffusion on the measured pseudo-first-order ion decay is measured and accounted for when estimating kf. Experiments were performed in the ranges 67–399 N m–2 and 365–530 K. At 300 K values of kf were found to be 4.52 × 10–29 and 1.33 × 10–28 molecules–2 cm6 s–1 for N+˙4 formation in N2 and (CO)+˙2 formation in CO, respectively. When expressed in the form kf=CTm, the values of m were found to be –3.8 ± 0.3 and –3.3 ± 0.2, a factor of two larger than the most recent literature values in each case.The equilibrium CO+˙2+ 2CO2rlarr;(CO2)+˙2+ CO2 was also observed for which the values of ΔH=–66.1 ± 2.9 kJ mol–1 and ΔS=–95.4 ± 4.6 J K–1 mol–1 were found, in good agreement with other literature values, leading to ΔHf[(CO2)+˙2]= 475.3 ± 2.5 kJ mol–1.The diffusion coefficients of N+˙2 in N2 and CO+˙ in CO were found to be almost identical, as were those of N+˙4 and (CO)+˙2 over the range of temperatures studied. The fact that the dimer ions have larger coefficients than the monomer is consistent with the role played by resonance charge transfer in the transport of ions. Temperature dependences are, on the whole, lower than expected from theory.

Molecular beam relaxation spectrometry of catalytic decomposition of single pulses of NH 3, on polycrystalline tungsten

In a study of reactive scattering of NH 3 single pulses on poly crystalline tungsten, molecular beam relaxation spectrometry (MBRS) was applied to a slow reaction. The experiments led to new understandings in settling the question of molecularity of surface reactions and surface species, which are precursors to the desorbing products. In the temperature range between 600 and 1300 K the reaction mechanism can be described as follows: NH 3(gas)→NH 3(a)→ k 1 NH∗ 3(a)→ k 2 NH (a) + 2 H (a) , ▪ NH∗ 3(a) + NH (a)→ k 3 N 2(gas) + 2 H 2(gas) , 2 H (a)→ k 4 H 2(gas) with the respective activation energies ( kJ/ mol): E 1 = 39.8, E 2 = 69.7, E 3 = 78.5, E 4 = 106.7. The frequency domain analysis of the pulsed mass spectrometer signals — recorded in the time domain by a signal averager — was carried out with a numerical fourier transform. Moreover, a new algorithm was developed based on the theory of fast Fourier transform (FFT) which shows sufficient transform characteristics for arbitrary non-band-limited functions.

Negative ion—molecule reactions at low collision energies

A pulsed mass spectrometer has been used to measure the rate constants of the following negative ion—molecule reactions ▪ as a function of temperature and ion kinetic energy from the thermal range to about 1 eV. Reactions (1), (2) and (5) were found to have rate constants which increase with increasing ion kinetic energy as well as with temperature. Reactions (3) and (4), on the other hand, have rate constants which decrease with energy and temperature.

Use of a pulse mass spectrometer to investigate the high-speed processes associated with the high-temperature decomposition of ammonium perchlorate

Use of a pulse mass spectrometer to investigate the high-speed processes associated with the high-temperature decomposition of ammonium perchlorate

Thermal Ion–Molecule Reaction Rate Constants at Pressures up to 10 torr with a Pulsed Mass Spectrometer. Reactions in Methane, Krypton, and Oxygen

A mass spectrometer for high-pressure ion–molecule reaction studies was constructed using a pulsed 4-keV electron beam and pulsed “gate-open” mass-spectrometer detection. The ions drift out of the field-free ion source by diffusion and mass flow. Pressures up to 10 torr can be used and the ion reaction times can be as long as several hundred microseconds. The system is specially suited for study of reactions with very small rate constants, long reaction sequences, and reactions dependent on third-body deactivation. Also when reverse reactions are operative the establishment of the equilibrium can be directly followed. The thermal rate constants for the reactions of Kr+ with CH4, and CH4+ and CH3+ with CH4, were measured. The reaction of O2+ with O2 to form O4+ is found to be third order, proceeding with a rate constant K = 2.8 × 10−30cm6molecules−2·sec−1 at 298°K. The activation energy for the reaction is negative and equal to 1–2 kcal/mole. The equilibrium constants for the reaction O2+ + 202⇄O4 + +O2 were determined over the temperature range 295°–350°K. A Vant Hoff plot of the equilibrium constant gives D(O2+–O2≃10 kcal/mole. The equilibrium constants and bond dissociation energy are in very good agreement with earlier results by Yang and Conway. Interesting comparisons with the N4+ formation in nitrogen can be made.

The study of the chemisorption of hydrogen on polycrystalline tungsten filaments by the flash method using a pulse mass spectrometer: (USSR)V N Ageev et al, Zh Tekhn Fiz, 34 (11), 1964, 2056–2066

The study of the chemisorption of hydrogen on polycrystalline tungsten filaments by the flash method using a pulse mass spectrometer: (USSR)V N Ageev et al, Zh Tekhn Fiz, 34 (11), 1964, 2056–2066

On the possibility of utilising a pulse mass spectrometer for the study of evaporation processes of complex materials: A. A. Mostovskii and D. A. Sakseev, Zh. Tekh. Fiz., 34 (7), 1964, 1321–1323. (In Russian)

On the possibility of utilising a pulse mass spectrometer for the study of evaporation processes of complex materials: A. A. Mostovskii and D. A. Sakseev, Zh. Tekh. Fiz., 34 (7), 1964, 1321–1323. (In Russian)

The application of the pulse mass spectrometer to the study of gaseous adsorption by the flash method

The application of the pulse mass spectrometer to the study of gaseous adsorption by the flash method

The application of the pulse mass spectrometer to the study of gaseous adsorption by the flash method: V.N. Ageev et al., J. Tech. Phys., 34 (3), 1964, 356–357

The application of the pulse mass spectrometer to the study of gaseous adsorption by the flash method: V.N. Ageev et al., J. Tech. Phys., 34 (3), 1964, 356–357

A Pulsed Mass Spectrometer with Time Dispersion

An improved design of a pulsed mass spectrometer using linear time of flight analysis has been completed. A peak width of two mass units at mass 40 has been achieved as well as a linear mass scale.