Three-stage Mass Spectrometer Research Articles

Radiative relaxation of vibrationally excited ions

A triple cell ICR spectrometer analogous to a three-stage mass spectrometer (MS/MS/MS) but capable of studying thermal energy collisions is described. The facility to store ions in a good vacuum allows the measurement of radiative lifetimes using a chemical reaction to probe the energy contents of the ions as a function of their storage time. Vibrational lifetimes have been measured for two diatomic ions in their electronic ground state: NO + and HCl +. NO + and NO have similar lifetimes, in very good agreement with calculated values. HCl + ( v = 1) has a lifetime ten times shorter than HCl (3 ± 1 ms compared with 29 ms), in fairly good agreement with the calculated value of 4.6 ms. This is the first experimental confirmation of the very short lifetimes predicted theoretically for diatomic hydride ions. Qualitative results have been obtained for the radiative lifetime of NH 3 +. The shape of the decay curves indicates the presence of long-lived (more than 300 ms) and short-lived (10–20 ms) states.

REMOTE MONITORING BY MASS SPECTROMETRY DURING ANAESTHESIA: Evaluation of a suitable inlet system

We describe a three-stage mass spectrometer inlet system suitable for use in operating theatres and evidence of its performance in delay and response times to step changes in oxygen and halothane concentrations. At 55 m and a sampled gas flow of 100mlmin-1, the inlet imposed a delay of 21s and prolonged the 10-90% response to 310ms for oxygen and 510ms for halothane. A linear relationship between inlet length and 10-90% response time at constant sampled gas flow was demonstrated for halothane but not for oxygen. Our results compared with those of other workers support the chosen compromise between practical flexibility and convenience versus maximum speed of response that was adopted in this system design.

A new three-stage mass spectrometer for high abundance sensitivity measurements

A three-stage mass spectrometer has been constructed consisting of two magnetic stages of 30-cm radius followed by an electrostatic analyzer with a radius of 43.25 cm. The instrument gives an abundance sensitivity of better than 1 × 10 7 and is used primarily for the isotopic analysis of uranium.

A computer-controlled, three-stage mass spectrometer

A computer-controlled, three-stage mass spectrometer for heavy element isotope ratio measurements has been constructed. The spectrometer consists of two symmetric, 90° sector, magnetic analyzers of 12-in. radius in a zero-dispersion configuration followed by a symmetric, 90°, cylindrical, electrostatic analyzer also of 12-in. radius. This arrangement yields an abundance sensitivity of 10 9. A small on-line computer directly controls the mass spectrometer and processes digital ion-counting data from it. Any scheme of scanning the magnetic field or ion accelerating voltage and accumulating data can be programmed through the computer.

1577. Cascade and three-stage mass spectrometer vacuum systems: J A McHugh and J C Sheffield,Rep KAPL-3382, Oct 1967, 20 pages (Sci Tech Aerospace Reps, 6 (12), 1875, N68-22625)

1577. Cascade and three-stage mass spectrometer vacuum systems: J A McHugh and J C Sheffield,Rep KAPL-3382, Oct 1967, 20 pages (Sci Tech Aerospace Reps, 6 (12), 1875, N68-22625)

Molecular Ion Dissociation by Thin Films

One of the fundamental limitations in mass spectrometry arises in attempts to differentiate betwoeen atomic and nuclear ions having the same charge to mass ratio. Partial dissociation of complex ions in a mass spectrometer has been observed. By using a three-stage mass spectrometer, complete dissoclation of molecular ions has been achieved. The film acts as a strong force field at a discrete point in the beam trajectory causing uncorrelated forces to act on the constituent atoms of the molecules. Further experiments are in progress utilizing these films as well as thin nickel films. (A.C.)