1. Spectroscopic Research of Pt + NH3
The Search for Polyatomic Molecules
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13200
Jamie Gengler, Timothy Steimle, and Jinhai Chen
Dept. of Chemistry & Biochemistry
Arizona State University, Tempe, AZ 85287
June 21, 2005
Funded by U.S. Dept. of Energy
Basic Energy Sciences

2. Motivations / Objectives
Characterize and model spectra obtained from polyatomic products of Pt + NH3.
Other polyatomic examples: SrNH2, SrCCH, SrNC (University of Waterloo group)
Anticipation of detecting the species PtNH or PtNH2.

3. Plasma Chemistry and Fluorescence Detection.
pre-amp
Gated photon
counter
20 Hz Nd:YAG
355 nm (10mJ)
PMT *
Optical filter
or Monochromator
Lens
IEEE computer
board # *
Platinum rod (rotated by stepper motor)
Molecular beam *
20 Hz solenoid pulsed valve
20% NH3
80% Ar
500 psi
Mirror
10-6 torr
diffusion pump
10-5 torr
diffusion pump
(variable time delay) CW
Titanium
sapphire
750 nm * *
D/A computer
board
Burleigh
wavemeter
RS232 serial
computer board 1
RS232 serial
computer board 2 #

4. Results of Previous Work.
K.Y. Jung, T.C. Steimle et al, J. Chem. Phys. 102 (2): Jan 1 4 3 2
Features 1 and 3 are unknown. Features 2 and 4 were assumed polyatomic in nature.

5. Results of Previous Work.
K.Y. Jung, T.C. Steimle et al, J. Chem. Phys. 102 (2): Jan
TABLE I. The predicted ab initio properties of PtN.
State Re(Å) Te(cm-1) we(cm-1) me(D)
X2P
a4S
A2S
b4D
B2D
C2D(II)
D2S
c4P
E2D(III)
d4P(II)

6. Unpublished Results. Low resolution spectra of Pt + NH3.
Other reagents (CH3CN, NO, N2, …) produce no spectra!
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Dispersed Fluorescence (next 2 slides)
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12435
13120
???
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12400

7. This molecule is probably PtN!
Unpublished Results.
Laser Line
Laser Line
945 cm-1 n1 n1
This molecule is probably PtN!

8. This molecule is probably PtN!
Unpublished Results.
Laser Line
Laser Line n1
940 cm-1 n1
This molecule is probably PtN!

9. Results of Previous Work.
K.Y. Jung, T.C. Steimle et al, J. Chem. Phys. 102 (2): Jan
TABLE I. The predicted ab initio properties of PtN.
State Re(Å) Te(cm-1) we(cm-1) we(cm-1)a me(D)
X2P
a4S
A2S
b4D
B2D
C2D(II)
D2S
c4P
E2D(III)
d4P(II)
a Observed value. E.J. Friedman-Hill and R.W. Field, J. Chem. Phys. 100 (9), May 1, 1994

10. This molecule cannot be PtN!
Unpublished Results.
Laser Line n1 n2 n3
Laser Line
210 cm-1
440 cm-1
650 cm-1 n1 n2 n3
This molecule cannot be PtN!

11. Pt Pt Platinum Dimer. ni = Ei – E0
where Ei = we(vi + ½) + wexe(vi + ½)2
Compare these to literature values:
we = 222 cm-1
wexe = 0.6 cm-1
M.D. Morse et al, J. Chem Phys., 115 (16), 7543 (2001)
we = 218 ± 21cm-1
wexe = -0.2 ± 5.7cm-1
Band near cm-1 has already been assigned as Pt2.
M.D. Morse et al, J. Chem Phys., 89 (9), 5517 (1988)

12. This molecule cannot be PtN!
Unpublished Results. n1 n2 n3 n4
Laser Line
Laser Line
445 cm-1
655 cm-1
877 cm-1
1095 cm-1 n1 n2 n3 n4
This molecule cannot be PtN!

13. Unpublished Results. 0.2 cm-1 13439.80 13440.50 195Pt 194Pt Natural
Abundances:
194Pt = 32.9%
195Pt = 33.8%
196Pt = 25.3%
198Pt = 7.2%
198Pt
196Pt
194Pt
195Pt
0.2 cm-1

14. Unpublished Results. Could this molecule be PtNHx? Pt + ND3 13440
13500
13400

15. Unpublished Results. Could this molecule be PtNHx? No!! Photon Counts
Pt + ND3
Photon Counts -1
Wavenumber (cm )

16. Platinum Dinitrogen? Obs. frequencies (in solid Ar):
cm-1 (n1), cm-1 (n2)
A. Citra et al, J. Phys. Chem. A 105, 7799 (2001)
2V = k1(DrNN)2 + k2(DrPtN)2 + k3(Df)2
445 cm-1 n2
In matrix form:
|GF – l| = 0
655 cm-1
2n3
877 cm-1
2n2
Calculated nitrogen isotope shifts:
Dn1 = cm-1
Dn2 = cm-1
Dn3 = cm-1
1095 cm-1
n2+2n3

17. Unpublished Results. Could this molecule be PtN2? No!! Photon Counts
Pt + 14NH3
Pt + 15NH3
Photon Counts
Wavenumber (cm-1)

18. Platinum Dimer.
M.D. Morse et al, J. Chem Phys., 89 (9), 5517 (1988)

19. Platinum Dimer. we/ ~ 187cm-1
Pt2 System VIII
0-0
1-0
13440 cm-1 Dispersed Fluorescence 2 4
we/ ~ 187cm-1
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wavenumber (cm-1)
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13700
wavenumber (cm-1)
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M.D. Morse et al, J. Chem Phys., 89 (9), 5517 (1988)
M.D. Morse et al, J. Chem Phys., 115 (16), 7543 (2001)

20. Results of Previous Work.
K.Y. Jung, T.C. Steimle et al, J. Chem. Phys. 102 (2): Jan
Pt2 System XVIII (n00 ~ cm-1)
3-0
4-0
we/ ~ 171 cm-1
18400
18500
18600
Laser wavenumber

21. Platinum Dimer Chemistry.
Pt2 (as well as PtN) spectra disappear unless NH3 is used. Why??
Proposed chemical chain reaction:
2Pt* + 2NH3 2PtN + 3H2
2PtN Pt2 + N DE ~ -5.22eV
2) Proposed metal cluster 3-body collision1 facilitated by NH3
chemisorption to Pt2:
2Pt* + :NH3
Pt*
:NH3
Pt*
Pt*
:NH3
Pt2 + NH3* (or fragments)
Pt*
Michael D. Morse, “Supersonic Beam Sources”, Experimental Methods in the Physical Sciences, 29B, 735 (1996)
M. Garcia-Hernandez et al, Surface Science, 430, 18 (1999)

22. Conclusions. PtN2 in abstract is actually Pt2.
First known metal dimer/cluster formation facilitated by a reagent (NH3).
Department of Chemistry
and Biochemistry