An integrated ion trap and time-of-flight mass spectrometer for chemical and photo- reaction dynamics studies

Abstract

We demonstrate the integration of a linear quadrupole trap with a simple time-of-flight mass spectrometer with medium-mass resolution (m/Δm ∼ 50) geared towards the demands of atomic, molecular, and chemical physics experiments. By utilizing a novel radial ion extraction scheme from the linear quadrupole trap into the mass analyzer, a device with large trap capacity and high optical access is realized without sacrificing mass resolution. This provides the ability to address trapped ions with laser light and facilitates interactions with neutral background gases prior to analyzing the trapped ions. Here, we describe the construction and implementation of the device as well as present representative ToF spectra. We conclude by demonstrating the flexibility of the device with proof-of-principle experiments that include the observation of molecular-ion photodissociation and the measurement of trapped-ion chemical reaction rates.

Design and characterization of a linear quadrupole ion trap for high-resolution Coulomb-crystal time-of-flight mass spectrometry

“…This leads to long flight times t and broad peaks. Ideally, the TOF extraction region should resemble a Wiley-McLaren setup with a two-stage acceleration region for obtaining a high resolution [18,21,35]. With the trap electrodes at ground potential during ion extraction, a Wiley-McLaren-type extraction region is not feasible.…”

“…In the TOF traps reported by Schowalter et al and Deb et al [18,21], all ion masses can be assigned from a single experiment but these setups require more complicated RF electronics. By comparison, the present approach relies on simpler electronics at the expense of an increased mechanical complexity.…”

“…Schowalter et al developed a LQT where the extraction field is applied directly to the trap electrodes [18]. This mass spectrometer featured a resolution of m/ m ≈ 50 and an improved version achieved m/ m ≈ 500 for trapped laser-cooled ions [19].…”

Laser-Cooling-Assisted Mass Spectrometry

“…1; similar to the apparatus previously outlined in Ref. 30). The LQT has a field radius of R 0 = 6.85 mm and is driven asymmetrically (two diagonally opposing electrodes at RF voltage V 0 , the others at RF ground) at a frequency of Ω ≈ 2π × 0.7 MHz and an RF amplitude of V 0 = 250 V.…”

Sympathetic cooling of molecular ions with ultracold atoms

“…If more sophisticated trapping geometries are devised that allow optical access, while retaining a truly quadrupolar field these techniques may become useful to the field). To overcome these limitations, we have developed a technique, where ions are radially ejected from a linear ion trap, similar to that proposed in [61], into a time-of-flight mass spectrometer (ToFMS) [62]. Further, if a laser-cooled atomic ion, which sympathetically cools all the trapped ions, is also present in the trap then the mass spectrum is dramatically improved; in fact, we have demonstrated mass resolutions m/ m > 1000 with a flight distance of only ∼ 30 cm [63,64].…”