Time-of-flight mass spectrometer TOFMS

The ionized part of the resulting cluster beam can be analyzed by a time of-flight mass spectrometer (TOFMS) which has been built up at 90° with respect to the beam direction. At the end the produced clusters land onto a substrate (generally a silicon single crystalline one) in a 10 mbar vacuum chamber. The substrate holder can be cooled down to 77 K. Several samples have been deposited at temperatures between 77 and 300 K. 

In order to identify the oxygen-carrying species responsible for the enhanced performance, it was decided to sample the converter gas phase by mass spectrometry. Since cesium can form suboxides with amu around 1,500 (CsjjOj) and because quadrupole mass spectrometers suffer from a transmission loss as the amu rises, a time-of flight mass spectrometer (TOFMS) was chosen. 

For the more volatile (alkali) metals it has been possible since the late 1970s to create a beam of cold, naked clusters of 1 < n < 100, where n is the number of atoms per cluster 348, 349). Metal vapor is produced in an oven and then cooled by expansion. The clusters are separated in a time-of-flight mass spectrometer (TOFMS). Later it became possible to handle less volatile (transition) metals through vaporization by a laser beam 347, 350-352). For the mass analysis the neutral clusters are photoionized by a suitable UV laser. 

A time-of-flight mass spectrometer (TOFMS) is an excellent instrument for these studies. The TOFMS produces approximately 10 spectra per sec. It is difficult to record individual mass spectra at this rate, but several data acquisition schemes see below) have been developed which record a finite number of discrete spectra. These techniques follow changes in peak intensity over millisecond intervals, thus recording the mass spectra of compounds whose residence time in the ion source is short. 

The TOFMS is a mass spectrometer that has the simplest and the fastest analyzing rate. All the components of samples can be analyzed in a few microseconds. A time-of-flight mass spectrometer (TOFMS) is mounted in the ICB setup in order to inspect the process in situ during deposition. A schematic diagram of the ICB-TOFMS is shown in Fig. 2. There are four main characteristics of the combined... 

Figure 3 is a highly schematic drawing of the experimental arrangement, which employs a laser ionization time-of-flight mass spectrometer (TOFMS) detector. 

The back end mass analysis is performed with an orthogonally configured time-of-flight mass spectrometer (TOFMS) built in house. Coupling these two temporally dispersive types of analyses, drift tube ion mobility and TOFMS, results in a very powerful analytical configuration since for every analysis cycle, a complete... 

Instrumentation for Analytical Chemistry gives rise to many abbreviations forming acronyms . These are often more encountered than the terms they abbreviate, and they appear extensively in the text. A reader new to the field may become lost or disoriented in this thicket of initials. To aid the student in reading the text, the Acronym Index below translates these and indicates the chapter and page where they are best defined or characterized. These acronyms are frequently compounded, as in UV/VIS (ultraviolet/ visible) or LC-CI-TOFMS (Interfaced Liquid Chromatograph to Time-of-Flight Mass Spectrometer operating in Chemical Ionization mode). The components of such compounded acronyms are listed individually in the index, but not aU the possible combinations. 

Thin films of polyPCN (PPCN) and poly TDCN (PTDCN) for electrical activity tests were prepared by the ionized cluster beam-time-of-flight mass spectrometer (ICB-TOFMS) deposition method [23] (see also the chapters by Z. Q. Xue and H. J. Gao in this book). 

Sturgeon, R.E., Lam, J.W.H., and Saint, A. (2000) Analytical characteristics of a commercial ICP orthogonal acceleration time-of-flight mass spectrometer (ICP-TOFMS). J. Anal. At. Spectrom., 15, 607-616. 

The mass spectrometer is a mass-flow sensitive device, which means that the signal is proportional to the mass flow dm/dl of the analyte, i.e. the concentration times the flow-rate. It is only now possible to realise the high (theoretically unlimited) mass range and the high-sensitivity multichannel recording capabilities that were anticipated many years ago. Of considerable interest to the problem of polymer/additive deformulation are some of the latest developments in mass spectrometry, namely atmospheric pressure ionisation (API), and the revival of time-of-flight spectrometers (allowing GC-ToFMS, MALDI-ToFMS, etc.). 

---