title: Development of a low-temperature photoelectron spectroscopy instrument using an electrospray ion source and a cryogenically controlled ion trap.
abstract: The ability to control ion temperatures is critical for gas phase spectroscopy and has been a challenge in chemical physics. A low-temperature photoelectron spectroscopy instrument has been developed for the investigation of complex anions in the gas phase, including multiply charged anions, solvated species, and biological molecules. The new apparatus consists of an electrospray ionization source, a three dimensional (3D) Paul trap for ion accumulation and cooling, a time-of-flight mass spectrometer, and a magnetic-bottle photoelectron analyzer. A key feature of the new instrument is the capability to cool and tune ion temperatures from 10 to 350 K in the 3D Paul trap, which is attached to the cold head of a closed cycle helium refrigerator. Ion cooling is accomplished in the Paul trap via collisions with a background gas and has been demonstrated by observation of complete elimination of vibrational hot bands in photoelectron spectra of various anions ranging from small molecules to complex species. Further evidence of ion cooling is shown by the observation of H2-physisorbed anions at low temperatures. Cold anions result in better resolved photoelectron spectra due to the elimination of vibrational hot bands and yield more accurate energetic and spectroscopic information. Temperature-dependent studies are made possible for weakly bonded molecular and solvated clusters, allowing thermodynamic information to be obtained.
authors.affiliation: Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99354, USA and Chemical and Materials Sciences Division, Pacific Northwest National Laboratory, MS 8-88, P.O. Box 999, Richland, Washington 99352, USA.
authors.forename: Xue-Bin
authors.initials: XB
authors.lastname: Wang
authors.forename: Lai-Sheng
authors.initials: LS
authors.lastname: Wang
mesh_terms: D000838:Anions; D002244:Carbon; D002621:Chemistry / Q000379:methods; D003080:Cold Temperature; D004867:Equipment Design; D006358:Hot Temperature; D007477:Ions; D007700:Kinetics; D008956:Models, Chemical; D008968:Molecular Conformation; D017785:Photons; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation* / Q000379:methods; D013053:Spectrophotometry / Q000295:instrumentation / Q000379:methods; D013696:Temperature; D013816:Thermodynamics
chemical_list: D000838:Anions; D007477:Ions; D002244:Carbon