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Flashcards in Exam 4 Deck (23):
1

LASER

Light
Amplification by
Stimulated
Emission of
Radiation

2

How a laser works:

1. excitation - energy is added to promote electrons to higher orbitals.
2. emission - electrons returns to lower energy source.
3. stimulated emotion - causes a photon to be released.

3

Advantages of Lasers

- high energy
- polarized
- coherent
- narrow bandwidth

4

Types of Lasers

1. solid state
2. gas
3. dye
4. semiconducting diode

5

Advantage and Disadvantage of semiconducting diode

+ small in size, cheap
- wavelength dependent on band gap

6

Population inversion

more electrons in higher energy state, than in lower energy state; necessary for a laser.

7

Examples of Lasers

YAG, Ruby

8

Order of Radiation from shortest wavlength to longest

gamma -> Xray -> UV -> infrared -> microwave -> radio

9

Analytical Applications of Lasers

- laser induced fluorescence
- raman scattering
- MALDI-TOF
- doppler effect
- CRD spectroscopy

10

Advantages of making instruments as small as possible

- saves lab space; makes room for more instruments
- portable; can use instruments in the field which leads to reduction of time spent in lab and cost

11

Disadvantages of making instruments as small as possible

short lifespan; which can impact reproducibility

12

Automation

reduces the amount of time needed for an analyst to go thru a number of samples

13

Can everything be automated?

NO

14

If it is a repetitive task....

it can be automated.

15

What are nanoparticle properties based on?

- composition
- size
- shape

16

Low angle light scattering

use laser to blast something and have light diffract off it; particle size is determined based off of light defraction

17

What is low angle light scattering used for?

to determine particle size

18

Brownian motion

particles move around in solution; causes an issue when viewing scatter of a laser

19

How do you view particles when they are moving?

- CCD cameras
- Photon counters

20

Dynamic light scattering

"photon correlation spectroscopy"
- uses doppler broadening of raliegh scattered light as result of brownian motion

21

Photosedimentation

measures the rate at which particles settle throughout a liquid; larger particles settle faster than smaller particles

22

5 Assumption of Photosedimentation

1. particle must be smooth, spherical
2. the final velocity of the particle must be reached instantly
3. all particles have same density
4. all particles are assumed to move independently
5. the fluid behaves as a continuum with a constant viscosity

23

Will all the stuff in water fall out of solution?

NO, not all stuff in water will fall out of solution.