The Popcorn-jet
Popcorn - Poppet controlled resistively heated nozzle
The popcorn-jet allows FTIR measurements of low-volatile compounds. The sample is melted onto molecular sieve pellets and enclosed between check-valves to avoid leakage during off-times. A gas pulse (0.3 s) from a 69 L reservoir picks up the sample and is supersonically expanded via a slit nozzle into a buffer volume (<0.5 mbar, 3.6 m3) [133]. The sample compartment and the nozzle can be heated individually up to 200 °C. Different nozzle geometries are available, a double 10 × 0.5 mm2 slit nozzle and an angled 60 × 0.2 mm2 slit nozzle. The gas pulse is probed by a synchronized scan of the FTIR spectrometer. For a typical spectrum 100-400 FTIR scans are coadded. For studying mixed clusters a highly volatile compound can be added via a coolable saturator prior to the reservoir.
Current projects
- Study of hydrogen bonding competitions between different acceptor sites (e.g. O—π, carbonyls)
- Improvement of the signal-to-noise ratio by variation of the nozzle geometry
- Design of a setup to study two low volatile compounds