Supporting information
Coverage dependent non-adiabaticity of CO on a copper surface
Takuma Omiya1,2 and Heike Arnolds1
(1) Surface Science Research Centre, University of Liverpool, Oxford Road, Liverpool L69 3BX,
United Kingdom; (2) Surface and Interface Science Laboratory, RIKEN, Wako 351-0198, Japan
1. Temporal and spatial overlap of all three beams
The mid-infrared and visible upconversion pulses generate a nonresonant (3) signal at 2IR+VIS,
which can be detected at 600 nm. This infrared-infrared-visible (IIV) sum frequency signal is reduced
by the pump pulse. Figure S1 shows the nonresonant IIV-SFG signal as a function of time delay
between pump and SF probe signal, together with calculated electron temperature convoluted by the
200 fs width of infrared pump pulse. The reduction in IIV-SFG follows the calculated electron
temperature and is likely caused by a temperature-dependent (3), similarly to the electron temperature
dependent (2) response observed for Cs/Ir(111) [1].
1.0
200
0.8
400
600
0.6
800
0.4
1000
electron temperature /K
norm. IIV SF signal
0
1200
0.2
0
1
2
3
delay time /ps
4
5
FIG. 1. Nonresonant IR-IR-visible sum frequency signal as a function of time delay between a 400 nm pump
pulse (absorbed 10 Jm-2) and femtosecond SF probe pulses. The solid line is the scaled convolution of the
electron temperature with a 200 fs probe pulse.
1
2. The effect of pump frequency and fluence
The dynamics of CO/Cu(110) were probed with different pump wavelengths and fluences. Germer et
al. [2] already reported a lack of pump photon energy dependence for CO on Cu(100). Figure S2
shows frequency transients of the C-O stretch mode of 0.77ML CO/Cu(110) with different pump
wavelengths. We calculated the electron and phonon temperatures using the modified two-temperature
model [3,4] using the known optical properties of copper and adjusted the incoming fluence of the
different pump wavelengths accordingly. Figure 2(left) shows that 400 nm, 532 nm and 800 nm pump
beams produce very similar transients which support the assumption that the transients are caused by
thermalized hot electrons and not nascent electrons. Figure 2(right) shows transients with different
pump fluence, which can be reproduced by the same el and lat.
0
-1
frequency shift /cm
frequency shift /cm
-1
0
-2
-4
-6
400nm
532nm
800nm
-2
-4
5J/m
-6
2
10J/m
2
-8
-8
0
5
delay time / ps
10
0
15
5
delay time / ps
10
15
FIG.2. Transient pump induced changes in the C-O internal stretch frequency for (left) different pump
wavelengths of 400 nm, 532 nm and 800 nm (absorbed fluence 10 J/m2) and (right) different absorbed pump
fluences of 5 J/m2 and 10 J/m2 (pump wavelength 532 nm) at 100 K. Solid lines are derived from calculated
electron and lattice temperatures and use the same coupling constants el and lat.
3. Coupling times derived from frequency transients
Figure 3 illustrates how different electron and phonon coupling times in equation 2 affect the
instantaneous adsorbate temperature (top graph) and the frequency shift calculated from the Bloch
equations (zero delay between infrared and etalon-shaped upconversion pulse), assuming a gradient of
0.04 cm-1/K. Calculation of electron temperature Tel and lattice temperature Tlat assumed an absorbed
fluence of 10 J/m2.
2
FIG. 3. Influence of electron and phonon coupling times. Top: instantaneous adsorbate temperatures
Bottom: frequency shift calculated from the Bloch equations.
3
4. Coverage dependent parameters
Coverage T2/ps
/cm-1
Frequency FWHM
gradient
gradient
a/cm-1K-1
b/cm-1K-1
el/ps
lat/ps
0.1 ML
1.1
9.6
0.0239
0.08
6.7
3.1
0.25 ML
1.4
7.6
0.0375
0.04
6.2
2.4
0.77 ML
1.2
8.8
0.0490
0.07
4.6
2.8
Values for T2 are determined from free induction decays,  is calculated from T2, the frequency
gradient is derived from steady-state measurements, the FWHM gradient is chosen to reproduce
the maximum FWHM and el and lat are obtained from fitting frequency transients.
Equations:
 cm 1 
10.6
T2 ps
 sim   0  a  (Tlat  100 K )
sim  0  b  (Tlat  100 K )
References
[1] I. M. Lane, Z. P. Liu, D. A. King, and H. Arnolds, Journal of Physical Chemistry C 111,
14198 (2007).
[2] T. A. Germer, J. C. Stephenson, E. J. Heilweil, and R. R. Cavanagh, The Journal of
Chemical Physics 101, 1704 (1994).
[3] E. Carpene, Physical Review B 74, 024301 (2006).
[4] J. Garduño-Mejía, M. P. Higlett, and S. R. Meech, Chemical Physics 341, 276 (2007).
4