1. Discrete-continuum interactions and lineshapes in the autoionization spectra of BH
Frauke Schroeder and Edward R. Grant
Department of Chemistry
University of British Columbia
Vancouver
Andrew T. Gilkison and C. Ricardo Viteri
Purdue University
West Lafayette
61st International Symposium on Molecular Spectroscopy
Ohio June 19 –

2. Motivation Few experiments on super excited states of molecules
Dynamics of autoionization
Characterization of continuum
BH: simple six electron system
model for new computational techniques
Intricate web of potential energy surfaces
Probing Rydberg series converging to BH+
 potential of BH+ X 2+ state
 potential energy surface of gateway state

3. Experiment (I): Laser excitation scheme3
Dye laser
FL2001
(ArF, 193 nm)
COMPEX
Excimer
Excimer
EMG 202
(XeCl,
308 nm) 2
BBO doubler
Dye laser
FL3002
skimmer
Turbo-
pumped vacuum
chamber
nozzle
1,2,3 linewidths  0.25 cm-1
5% B2H6 in
3 atm H2 1
OPO
Panther
Nd:YAG
PL8000
(355 nm)

4. Experiment (II): Timing and ion detection
preamp
(gain = 10)
scope
sample and photolysis
1.5 ms later: excitation
50 ns later: +400 V pulse
ion signal amplified and digitally recorded
MCP PC
(Labview)
TOF-MS
Extractor grid
gas flow
Repeller grid
photolysis laser
excitation lasers
pulser (+400 V)

5. Excitation Routes v+
v+ + 1 w3 w2 w1

6. Rydberg Formula Approximate estimation of energy positions: BH+ X 2+IP
electronic
energy
levels
Approximate estimation of energy positions:
BH+
X 2+

7. Vibrational autoionization spectra

8. Third Photon Excitation
V+=V’+1 V’
V+=V’-1
V+=V’
B 1+
X 2+
below
threshold

9. Vibrational autoionization spectra

10. Third Photon Excitation
V+=V’+1 V’
V+=V’-1
V+=V’
B 1+
X 2+
below
threshold
above
threshold

11. Vibrational autoionization spectra

12. Fano Formalism
Discrete state embedded in an underlying continuum are analyzed by the Fano formalism: ER
q = 2
q = 
q = 0
q = -2
and
Intensity [a.u.]
E [cm-1]

13. Analysis of experimental results
Discrete state embedded in an underlying continuum are analyzed by the Fano formalism:
and
 Analysis of the spectra with
respect to this formulism
provides values for  and q.

14. Overall trends in line shapes
Below threshold
Above threshold
 decreases with increasing n
 increases with increasing v+
no significant change in magnitude

15. Overall trends in line shapes
Below threshold
Above threshold
q increases with increasing n
change in magnitude except for v+ = 2
but: change in sign from below to above threshold!!!

16. Line shapes below and above threshold
BH+ X 2+ v+ = 2 from BH B 1+ v‘ = 2
BH+ X 2+ v+ = 2 from BH B 1+ v‘ = 1

17. Line shapes in terms of Fano formalism
Discrete state embedded in an underlying continuum are analyzed by the Fano formalism:
and
where:
and

18. Franck-Condon Factors
Estimation of Franck-Condon Factors possible from equations for q
Assumption:
V is calculated from experimental linewidths:
…analog for qabove v+ v‘ 1 2 3 4
0.90
0.18
-0.30
0.67
0.60
-0.61
0.54
-0.39
0.46
0.72

19. Contribution of Franck-Condon factors to qv+
below
above 1
-2.23
0.20 2
-0.88
0.88 3
-1.19
1.00 4
1.56

20. Franck-Condon Factorsv+ v‘ 1 2 3 4
0.90
0.18
-0.30
0.67
0.60
-0.61
0.54
-0.39
0.46
0.72

21. Interloper 7s (N+ = 1) 8p (N+ = 0; v+=4) 6s (N+ = 1; v+=6) 6p (N+ = 2)

22. Conclusions
Triple resonance spectroscopy isolates high-Rydberg states of BH converging to v+ =
Lineshapes are well characterized by Fano formalism. Trends are explained: (v), sign of q, window resonances, etc. 2 v+ v‘ 1 3 4
0.8985
0.1820
0.6737
0.5953
0.5408
0.5433
0.4640
0.7229
Estimated Franck-Condon factors show higher values for
off-diagonal elements for v‘ and v+ > 1.
Interlopers indicate large interactions between vibrational series and huge differences in electronic potentials B of BH and X of BH+.

23. Acknowledgments Thank you for your attention! Prof. Edward Grant
C. Ricardo Viteri
Thank you for your attention!

24. Next:. Dynamics of dissociative recombination,. electron loss and
Next: Dynamics of dissociative recombination, electron loss and isolated-core photon absorption in single rovibronic Rydberg resonances of 11BH
C. Ricardo Viteri and Andrew T. Gilkison
Department of Chemistry
Purdue University
West Lafayette
Scott J. Rixon and Edward R. Grant
University of British Columbia
Vancouver
61st International Symposium on Molecular Spectroscopy
Ohio June 19 –