1. Laser Induced Fluorescence Spectroscopy of the Jet-Cooled Transient Species AsD2 and AsHD
Bob Grimminger and Dennis Clouthier
Department of Chemistry, University of Kentucky, Lexington, KY
I think it would look better if this slide had the same border etc. as the others
Talk is OK, but a little thin for 15 min. Perhaps you could add to it by discussing predissociation mechanism
In 1 slide and compare NH2, PH2, AsH2 in another near the end.

2. Motivation
AsH3 is used in many semiconductor processes but species involved are not well understood
Dixon et al. (Proc. Roy. Soc. A. 305, 271 (1968)) only partially studied AsD2 at low resolution
Continuation of AsH2 study by Clouthier group
Measurement of new vibrational frequencies of interest

3. Production of jet-cooled radicals
Precursor gas mix:3% AsD3 in Ar
Argon mixed with our precursors, in this case Arsine, is allowed to pass through a (slightly modified) general series 9 pulsed valve. The valve opens when current is passed through the solenoid housed in the body, causing the magnetic armature to move up.
As the gas passes between the electrodes, a discharge is struck. This begins the processes that create the radicals and other species of interest
The reactions continue as collisions occur in the reheat tube. Adjusting the reheat tube length can therefore affect the signal intensity
After the gas expands into the chamber, it is probed with laser light
Explain how you made AsHD

4. Preliminary information
Ground state constants known from microwave study (H. Fujiwara and S. Saito, J. Mol. Spec. 192, 399 (1998).)
Excited state constants for AsH2 isotopologue known from previous work in Clouthier lab (S.-G. He and D. J. Clouthier, J. Chem. Phys. 126, , (2007).)
Estimate of origin from previous AsD2 study
Arsenic has a nuclear spin of 3/2
Near oblate in ground state; near prolate in excited state

5. Vibronic analysis of AsD2 LIF spectrum
Need to identify that this is AsD2 not AsHD, perhaps in title What are other bands beyond cm-1 and what is band to the blue of 2(3-0)?
Parameter
Observed
Calculated
ω1 (cm-1)
1679.8
ω2 (cm-1)
612 (2)
613.7
ω3 (cm-1)
1600.1
B3LYP/Aug-cc-pVTZ

6. High resolution spectrum of the 0-0 band
Experimental
Simulation from fit
140 wavenumbers.
Intensity changes due to predissociation
Prefer 0-0 or 0_0^0 to band origin
Perhaps you should identify some of the various subbands and talk about difficulty of assigning spectrum in which there are few regularities

7. Comparison of excited state rotational constants
Excited state parameter
AsD2
AsH2
A (cm-1)
(5)
(13)
B (cm-1)
(2)
(6)
C (cm-1)
(3)
(6)
εaa (cm-1)
2.329 (3)
4.718 (4)
εbb (cm-1)
(15)
0.082 (3)
εcc (cm-1)
(19)
(3)
εaa/A
(3)
(4)
εbb/B
(2)
(3)
εcc/C
(1)
(8)
Just as a check of the measured constants
Do you mean Comparison of excited state constants?

8. Ground and excited state geometries
Ground state geometry determined by microwave study
Excited state geometry refined from observed rotational constants from both isotopologues
Coordinate
Ground statea
Excited stateb
As-H (Å)
(6)
1.483 (5)
H-As-H (degrees)
90.79 (8)
122.9 (2)
The calculated geometry uses rotational constants from both rotationally fit isotopologues
How about Ground and excited state geometries
a H. Fujiwara and S. Saito, J. Mol. Spec. 192, 399 (1998).
b This work.

9. Resolved resolved hyperfine splittings
Title: Resolved hyperfine splittings

10. Hyperfine constants in the excited state
Show splittings caused by spin and then splittings caused entirely by hyperfine
Parameter
AsD2
AsH2
aF (As) (cm-1)
.0567 (11)
.0511 (14)
aa1 (As) (cm-1)
(28)
bb1 (As) (cm-1)
(36)

11. Single level emission from AsD2
Ka´ = 1
Ka´´ = 2
Ka´´ = 0
Only observed bending mode.
Peaks are split due to the delta Ka selection rule
ω2 = 707 (1) cm-1
x22 = -2.0 (2) cm-1

12. Single level emission from AsHD
ω2 = (8) cm-1
x22 = -4.0 (2) cm-1
We wanted to add to the available knowledge about the AsH2 system, so we looked to find evidence of the assymetric stretch with the
Very small indication of the stretching vibrations in combination peaks with the bend vibration, but the very large calculated x12 and x23 values indicate that measuring them would not give an accurate harmonic frequency

13. Ground state vibrational frequencies for various isotopologues
Parameter
AsH2a
AsD2b
AsHDb
ω1 (cm-1) (observed)
(9) --
(calculated)
2172.6
1546.3
2178.3
ω2 (cm-1) (obs.)
984.4 (6)
707 (1)
862.4 (8)
(calc.)
1003.5
714.7
871.1
ω3 (cm-1) (obs.)
2184.1
1555.3
1550.9
Discuss what the point of measuring AsHD vibrations. Include reference to working out the force constant matrix from vibrational frequencies, and comparing to the published force constants from centrifugal distortion coefficients.
Title: Ground state vibrational frequencies for ….
a Previous Clouthier study
b This work

14. Geometry comparison of isovalent species
Parameter
NH2a
PH2a
AsH2b
Ground state
Angle (deg.)
103.4
91.7
90.79 (8)
Bond length (Å)
1.024
1.418
(6)
Excited state
144
123.2
122.9 (2)
1.004
1.389
1.483 (5)
a D. A. Ramsay in Spectroscopy of the Excited State, edited by B. Di Bartolo (Plenum Publishing Corp., New York, 1976) p. 66.
b Fujiwara (1998) and this work.

15. Conclusions
Accurate determination of the excited state constants of AsD2, allowing for the refinement of the excited state geometry
Determination of bending vibrational frequencies of AsD2 in ground and excited states
First reported spectra of AsHD
Refinement rather than recalculation
Determination of bending vibrational frequencies in the ground and excited? states of AsD2 and AsHD
First reported spectra of AsHD
Can you have another slide before this comparing the ground and excited state structures of NH2, PH2 and AsH2 – in other words, what does it all mean?