Molecular spectroscopy and reaction dynamics Group III Sigtryggur Bjarki Sigtryggsson Styrmir Svavarsson Úlfar Þór Björnsson Árdal

Resonance Enhanced Multiphoton Ionization-Time of Flight (REMPI-TOF)

History The phenominon of two photon adsorption was first reported by Maria Geoppert-Mayer in 1931 First used in 1978 by two research groups: Boels in Germany Antonov in Russia Has since been of great importance for the scientific community and resulted in many breakthroughs in molecular spectroscopy

Theory REMPI-TOF uses a high intensity laser to excite molecules (usually small molecules) and atoms. Because of the high intensity of the laser the molecule/atom can absorb more than one photon wich equal a energy difference between two distinct energy levels. The virtual state is a very short lived and non-observable state For each photon absorbed the change in electronic angular momentum can be either 0 or ±1. If there are more then one photon absorbed the change in electronic angular momentum can be more than ±1.

In the (2+1)REMPI-TOF there are two photons used to excite the molecule/atom and one photon used to ionize the particle. After the ionization the particle is accelerated in an electric field and travels to a detector over a fixed distance. The time from ionization to detection is the time of flight (TOF) of the particle.

The equipment

Graph 1

Graph 2

Excited States Ground States Configuration Term J Level (cm-1) 4s24p5 3/2 1/2 3685 Excited States Configuration Term J Level (cm-1)  4s24p4(3P1)5p  2D° 5/2 78511 3/2 78676 4D°  1/2 78860 4s24p4(3P2)5p  75695  4P° 75815

A+ + e B+ + e E AB AB+ + e AB** A + B+ AB # # A+ + B A + B/B* 1xhn 2xhn

HCl/DCl

A typical day at the office