Laser double optical resonance excitation-ionization of Mo with optogalvanic detection

Hu Lu,Lazaros Varvarezos,Emilio Mariotti,Alberto Andrighetto,Piergiorgio Nicolosi,John T Costello,Daniele Scarpa

doi:10.1088/1402-4896/ac48a7

Abstract

We report on the first measurement of resonant three-step, two-colour ionization of atomic molybdenum, using a hollow cathode lamp (HCL) with optogalvanic detection. Wavelength scans were made for two specific transitions involved in the ionization pathways under investigation, namely 4d5(6S)5s 7S3–4d5(6S)5p 7P4 and 4d5(6S)5p 7P4–4d5(6S)6d 7D5. So-called ‘slow’ and ‘fast’ optogalvanic signals were respectively observed for each resonant quantum jump and for the simultaneous excitation of the two laser frequencies. This successful detection confirms the HCL as a cost effective spectroscopic investigation tool. In particular its use in the optogalvanic mode of operation allows one to precisely, easily and reliably tune the wavelength of one or more lasers to resonances of interest for experiments in the general domain of atomic vapour laser isotope selection (AVLIS). This activity has been undertaken in the framework of the Selective Production of Exotic Species (SPES) project at the ISOL facility of the Legnaro National Laboratories of INFN. These measurements are a necessary step towards the realization of the MOLAS subproject of SPES, whose aim is to verify the production of 99m technetium for medical application via laser ionization of the 99 uma isotope of Molibdenum.

Highlights

The resonance ionization laser ion source (LIS) [1, 2] technique is versatile and widely applied in isotope separator on-line (ISOL) facilities [3,4,5,6,7] where several radioactive ionic species are normally delivered to the target area for study
Photographs of the slow and fast optogalvanic signals on the oscilloscope screen are shown in figure 2, along with a partial energy level diagram illustrating the possible ionization pathways using data from [20]
A few papers have described the interaction of Mo with light, especially in the IR—UV range

Summary

Introduction

The resonance ionization laser ion source (LIS) [1, 2] technique is versatile and widely applied in isotope separator on-line (ISOL) facilities [3,4,5,6,7] where several radioactive ionic species are normally delivered to the target area for study. Due to its elemental specificity, LIS is employed in order to produce ion beams exhibiting selective physical composition such as mass and charge state. By carefully tuning the photon energy of the laser(s), stepwise single and/or multicolour resonant excitations are induced resulting in atomic ionization [8, 9]. Since the electronic structure of each atom is unique, such ionization schemes are naturally elementselective and can even form the basis for schemes leading to isotope selection of a particular element. Several off-line laboratories carry out investigations in order to develop efficient ionization schemes, tailored for different elements [11, 12]

Methods

Results

Conclusion