New Method to Study Ion-Molecule Reactions at Low Temperatures and Application to the H2+ + H2 → H3+ +H Reaction

被引:62
作者
Allmendinger, Pitt [1 ]
Deiglmayr, Johannes [1 ]
Schullian, Otto [1 ]
Hoeveler, Katharina [1 ]
Agner, Josef A. [1 ]
Schmutz, Hansjuerg [1 ]
Merkt, Frederic [1 ]
机构
[1] Swiss Fed Inst Technol, Lab Phys Chem, Vladimir Prelog Weg 2, CH-8093 Zurich, Switzerland
基金
瑞士国家科学基金会;
关键词
cold and ultracold reactions; deceleration; deflection; ion-molecule reactions; Rydberg states; COLLISIONS; SCATTERING; DYNAMICS; BEAM;
D O I
10.1002/cphc.201600828
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Studies of ion-molecule reactions at low temperatures are difficult because stray electric fields in the reaction volume affect the kinetic energy of charged reaction partners. We describe a new experimental approach to study ion-molecule reactions at low temperatures and present, as example, a measurement of the H2+H2+H reaction with the ion prepared in a single rovibrational state at collision energies in the range E-col/k(B)=5-60K. To reach such low-collision energies, we use a merged-beam approach and observe the reaction within the orbit of a Rydberg electron, which shields the ions from stray fields. The first beam is a supersonic beam of pure ground-state H-2 molecules and the second is a supersonic beam of H-2 molecules excited to Rydberg-Stark states of principal quantum number n selected in the range 20-40. Initially, the two beams propagate along axes separated by an angle of 10 degrees. To merge the two beams, the Rydberg molecules in the latter beam are deflected using a surface-electrode Rydberg-Stark deflector. The collision energies of the merged beams are determined by measuring the velocity distributions of the two beams and they are adjusted by changing the temperature of the pulsed valve used to generate the ground-state H-2 beam and by adapting the electric-potential functions applied to the electrodes of the deflector. The collision energy is varied down to below E-col/k(B)=10K, that is, below E-col approximate to 1meV, with an energy resolution of 100eV. We demonstrate that the Rydberg electron acts as a spectator and does not affect the cross sections, which are found to closely follow a classical Langevin-capture model in the collision energy range investigated. Because all neutral atoms and molecules can be excited to Rydberg states, this method of studying ion-molecule reactions is applicable to other reactions involving singly charged cations.
引用
收藏
页码:3596 / 3608
页数:13
相关论文
共 51 条
[1]   Surface-electrode decelerator and deflector for Rydberg atoms and molecules [J].
Allmendinger, P. ;
Deiglmayr, J. ;
Agner, J. A. ;
Schmutz, H. ;
Merkt, F. .
PHYSICAL REVIEW A, 2014, 90 (04)
[2]   Deceleration and trapping of a fast supersonic beam of metastable helium atoms with a 44-electrode chip decelerator [J].
Allmendinger, P. ;
Agner, J. A. ;
Schmutz, H. ;
Merkt, F. .
PHYSICAL REVIEW A, 2013, 88 (04)
[3]   Quantum scattering calculations on chemical reactions [J].
Althorpe, SC ;
Clary, DC .
ANNUAL REVIEW OF PHYSICAL CHEMISTRY, 2003, 54 :493-529
[4]   THE EFFECT OF VIBRATION AND TRANSLATIONAL ENERGY ON THE REACTION DYNAMICS OF THE H-2+ + H-2 SYSTEM [J].
ANDERSON, SL ;
HOULE, FA ;
GERLICH, D ;
LEE, YT .
JOURNAL OF CHEMICAL PHYSICS, 1981, 75 (05) :2153-2162
[5]   A 3-DIMENSIONAL QUANTUM-MECHANICAL STUDY OF THE H2+H2+ SYSTEM - CALCULATION OF REACTIVE AND CHARGE-TRANSFER CROSS-SECTIONS [J].
BAER, M ;
NG, CY .
JOURNAL OF CHEMICAL PHYSICS, 1990, 93 (11) :7787-7799
[6]   Ion-molecule chemistry at very low temperatures: cold chemical reactions between Coulomb-crystallized ions and velocity-selected neutral molecules [J].
Bell, Martin T. ;
Gingell, Alexander D. ;
Oldham, James M. ;
Softley, Timothy P. ;
Willitsch, Stefan .
FARADAY DISCUSSIONS, 2009, 142 :73-91
[7]   Low-temperature Collisions between Neutral Molecules in Merged Molecular Beams [J].
Bertsche, Benjamin ;
Jankunas, Justin ;
Osterwalder, Andreas .
CHIMIA, 2014, 68 (04) :256-259
[8]   Stationary flow conditions in pulsed supersonic beams [J].
Christen, Wolfgang .
JOURNAL OF CHEMICAL PHYSICS, 2013, 139 (15)
[9]   Quantum theory of chemical reaction dynamics [J].
Clary, DC .
SCIENCE, 1998, 279 (5358) :1879-1882
[10]   Rates of complex formation in collisions of rotationally excited homonuclear diatoms with ions at very low temperatures: Application to hydrogen isotopes and hydrogen-containing ions [J].
Dashevskaya, EI ;
Litvin, I ;
Nikitin, EE ;
Troe, J .
JOURNAL OF CHEMICAL PHYSICS, 2005, 122 (18)