Download CHEM-4511-32

CHAPTER 20: FIGURE 20A.1
MATTER, AND
CHANGE AND
2E| PETER
ATKINS|
JULIO ATKINS
DE PAULA
PHYSICAL CHEMISTRY: QUANTA,
THERMODYNAMICS,
STRUCTURE,
CHANGE
10E | PETER
|
| RONALD
FRIEDMAN
JULIO
DE PAULA
Microfluidic “alcove” type mixing device
-200
-180
-160
-140
Inlet 1
-120
-100
-80
-60
-40
Y (µm)
-20
0
20
Inlet 2
40
60
80
100
120
140
160
180
10 µm
200
-300
-250
-200
-150
-100
-50
0
X (µm)
Mixing time (flow at 120 ml/min) : ~100 ms
Mixing time by diffusion: ~15 ms
50
100
150
200
250
300
CHAPTER 20: FIGURE 20A.2
MATTER, AND
CHANGE AND
2E| PETER
ATKINS|
JULIO ATKINS
DE PAULA
PHYSICAL CHEMISTRY: QUANTA,
THERMODYNAMICS,
STRUCTURE,
CHANGE
10E | PETER
|
| RONALD
FRIEDMAN
JULIO
DE PAULA
Ultrafast kinetics via “pump-probe” technique
Goal:
Follow temporal evolution of a molecular system at well-defined times after
photoinitiation of a reaction.
Pump-probe spectroscopy:
1. Excite sample with light pulse #1
2. Wait time Dt
3. Measure system response with light pulse #2
Dt
System response
1
2
Ultrafast kinetics via “pump-probe” technique
Nanosecond pulses: electronic delay
Pico-/femtosecond pulses: optical delay line
feste
Verzögerungsfixed
distance
Strecke
Time difference for the pulses
d1
Dt = (d2 – d1)/c
c = 3·108 m/s
d2
variable variable
distance
VerzögerungsStrecke
t
 Dd = 0.3 mm  Dt = 1 ps