1 Zeeman patterns in FT resolved fluorescence spectra of NiH Amanda Ross, Patrick Crozet, Heather Harker and Cyril Richard Laboratoire de Spectrométrie Ionique et Moléculaire (LASIM), Université Lyon 1 & CNRS, Villeurbanne, France. and Stephen Ashworth School of Chemistry, University of East Anglia, Norwich NR4~7TJ,UK Illustrating electronic structure variations in Doppler-limited spectra. 0,72 T 0.13 T 0 T cm -1

2 FT Zeeman experiment. LIF + Nd-Fe-B magnets External magnetic field fluorescence  Linearly polarised laser beam FTS Polariser (optional) Cu anode Ni cathode Adjustable gap

3 Zero-field NiH fluorescence spectrum (FT) Isotopic selection is possible. Res cm -1, Rec. time 2 hrs. Abundant rotational relaxation in B state. Strong, collisionally induced fluorescence

4 Emission from excited states E ~17400 cm -1 in NiH Observe fluorescence from  to spin-orbit mixed,     and   states. Laser pumps a chosen J and parity (sometimes) level of v=1, B 2  5/2 58 NiH Collisional energy transfer populates many more! Q1: Are the Zeeman patterns useful? Q2 : Can we model them? Q3: Is this process M J selective? Emission to X 2  5/2, v=0-3 E cm -1

5 Some lines show more ‘potential’ than others R branch, B-X 1 58 NiH, observed as rotational relaxation when laser pumped Q(2½) B-X 1. Resolution = cm -1, field = 0,72 T

6  The strongest line in the spectrum Q(2½) B 2  5/2 -X 1 2  5/2 happens to have unresolved M J structure (and  doubling)  M J = 0, ±1   M J = 0  M J = +1     Dispersed fluorescence shows all allowed transitions  M J = -1 Convenient for magnetic field calibration! LASER

7 Pumped Q(2 ½)  M J =0 B= 7200 Gauss cm -1 Calc.  M J =±1 P(3½) [1-0] line, B 2  5/2 –X 2  5/2 58 NiH Calc  M J =0 FTS, ~ Doppler limited spectrum Landé factors are known : McCarthy et al JCP (1997)‏ +1/2 -3/2 +3/2 +5/2 +7/2 -1/2 -7/2 -5/2 -3/2 -1/2 +1/2 +3/2 M J " -1/2 +1/2 -5/2 +5/2 +3/2-3/ cm -1 MJ"MJ"

8 Can we select M J components ? P(3½) B-X 1    again Near laser, to v"=0 Transition to X 1 v"=2 Populate all M J’ - 2½ ≤ M J' ≤  2½ Popu1ate all M J ’ except M J  2½ Laser (scatter) Populate only M J ' =  2½ M J " =  3½  1½  2½ 0.72 T 0.73 T Caveat :even uglier because of the onset of  doubling

9 M J is enhanced even after collisions (J+1) within a given state 0.7 T

10 Simplify by recording fluorescence through a polarizer. Example : collisionally induced fluorescence, R head, F 2  7/2 -X 1 2  5/2 R(J")  M J = 0  M J = ± 1  M J = 0, ± 1

11 Another example where the polariser really helps P(3½) B 2  5/2 – X 1 2  5/2 P(3½) I  – X 2 2  3/2   all  M J 0, ± 1 can be distinguished for some ‘new’ transitions

12 Zeeman structure does not always collapse at high J Example : P branch, I – W 2  3/2  P f (6½)‏ P e (6½)‏ 0.72 Tesla

13 Any new results ? 58 NiH : extension to v" =1, 2 in X 1 2  5/2, X 2 2  3/2 and to v=1 in the W 1 2  3/2 state. 60 NiH : a lot of measurements … Fit ~ 1100 transitions (from 2 spectra) to simple expression to find T, g eff (J, parity) Effective Landé factors g eff can be predicted from the Field group Supermultiplet model (zero field fit) & Zeeman Matrix.

14 Spin-Orbit Coupling + L and S uncoupling off diagonal matrix elements  v  0 Idem x FC factors Current fit status : unstable ! Supermultiplet model given by Gray et al, J. Chem. Phys (1991)

15 Zeeman matrix, at given J.  1/2  3/2  3/2  5/2   g s     (6/2).   J(J+1)- 3/4    1/2  g s   g s   J(J+1)-3/4  2   J(J+1)-15/4   3/2  g s    g s   J(J+1)-15/4  2  3/2  g s     5/2  g s  

16 Satisfactory outcome … Example, W 1, 2  3/2   v=0 2   v=   v=0 66   v=1 1   v=   v=   v=2 2   v=2 8 % Composition Parity e f e   f P e ( 5½) I – W 1 (0-0) P f (5½)

17 Comments, Conclusions and Acknowledgements Isotopic selectivity is a real advantage. Collecting all data in identical conditions is great! S/N ratio is a problem, particularly with single M J selection Polariser alignment is critical. Analysis is the rate determining step. We are grateful to the CNRS and to ANR for the financial support received for this project. Many thanks for comments, encouragement and suggestions from R. Field, D. Tokaryk, C. Linton, T. Steimle, A. Ariste- Lopez …

18 More examples in collisionally induced systems Q branch of F 2  7/2 -X 1 2  5/2 and R branch of A 2  5/2 -X 1 2  5/2 Analysis of Zeeman structure gives g ~ 3 for F 2  7/2, as expected; but g ~ 2 for A 2  5/2. Already established by RWF and coworkers … 0.71 Tesla Zero field Resolution 0.02 cm scans – cm -1