Instrumental Chemistry

• Silicon Carbide rod, with cooled contact to prevent arcing.
• Arching is the breakdown of a gas that cause the electrical discharge
• range 4 000 to 200 cm1 is

a roll of tightly wound wire that is heated electrically but has low intensity

Rod of lanthanide ( rare earth oxidant) with platinum leads

reflective optical component with a series of closely ruled lines

higher energy states have a higher population than lower energy states

• Light amplification stimulating emission radiation. 
• laser has
• stimulate emission= styimulating a molecules to emit a photon and return to the ground state
• directionality, linearity, and are monochromatic.
• The components lasing source, optical cavity, and an output source.
• Most common laser is the ruby laser and it is in the visible light region ~700nm.
• isolate line of one wavelength
• coherent- all wavelengths of light are in phase with one another
• Population inversion

black bodies emits as much radiation as they release because they must maintain their temperature.

• Ability to distinguish between two peaks 
• greater the resolution the better discrimination between two wavelengths
• the expense of resolution is decreasing the signal to noise ratio due to decreasing of the exit slit

The ability to distinguish angular separation af adjacent wavelengths

• Wavelengths outside the bandwidth expected by the monochromator.
• light scattering from optical components and walls. It can also come from outside if the sample is not sealed properly

emits electron from a photosensitive, negatively charged surface(cathode) when struck with visible or ultraviolet light. These electron flow to an anode whose current is proportional to the radiation intensity.

Produce an electrical signal when struck by photons

D2 to dissociateand emit ultraviolet radiation from 110 to 400 nm

• Source of continuous visible ( entire VIs spectrum) but also some UV and NIR
• range 320 to 2 500 nm

• Photmultiplier tubves scan slowely throught the soctrum one wavelength at a time
• sensitive device
• electron are emitted from a [photosensitive surface to a second surface called a dynode ( which is positive with respect to the photosensitive emitter). There are a series of dynodes. The dynode accelerated the electrons and more electrons are knocked of from the dynode with each hit.
• electrical signal proportional to the to irradiance

• Multiplexing 
• throughput

Only one type of wavelength comes in at once.

• core: silicon n and p type, this creates a serries of pn junctions The more radiation that strike the junction the less charge remains at the end of the measurment
• all wavelengths are recorded simultaneously.
• Major benefit is fast spectral acquisition.
• FAST !!
•  records the entire spectrum at once within the fraction of a second.
• faster acquisiton and higher signal tot noise ration or some combination of both

• Charge coupling device
• stores photosensitive charge in a 2D array
• made of p-doped Si and an n-doped substrate

A negatively charged surface that has photosensitive abilities that allow it to emit a photo-electron when it is struck by a a photon.

range of frequencies in a band of wavelengths.

• Range: UV Vis and NIR 
• simulate sunlight

The voltage that is developed between the junction is proportional to the temperature difference

• These are made specific to the element and they enhance emission intensity
• They emit light is specific to the metal that is used as the cathode.

TGS (triglycine sulfate) has permanent electrical polarization because of the alignment of molecules in a crystal.

Source⇒ Monochromator⇒Sample⇒Detector⇒signal readout amplifier

• When one absorbing species is converted to another, it is apparent on the absorption spectrum
• The wavelength where the absorption spectrum of a converting species overlap. It is a good evidence that two principal species are present.

• Binding depends on the concentration of the components
• graph of product over the changing reactant [PX]/[x] versus [x] and we get a slopoe of -K

• Make sure that the species follow Beer's Law
• make sure that the species have the same ionic concentration and pH 
• Make sure that their wavelength maximum happen at the same mole fraction for each 
• Measure the mixture at different wavelengths.
• measure at different concentrations
• K reasonable greater than 1
• Only a single equilibrium 
• constant volume

• Allows for the determination of the stoiciometry of the predominant products
•  this method can be used when various complexes can form between two species.

Guess: entire spectrum is collected at one with the photo diode array but a spectrophotometer with a photo-multiplier will scan one wavelength at a time (scanning spectrometer.)

grating has linear dispersion, while the prisim does not

• measuring the equilibrium constant 
• (scatchard plot)

• P/P0
• A=-logT=ebc

• deuterium arc lamp that emits in the range 200 to400 nm.
• Used in the Uv-Vis spectrophotometer

interferometer is at the heart of the

• 1) take the absorbance spectrum og bothe analytes
• 2) measure the epsilon wavelength peaks
• 3) measure the absorbance at the lammbda maximums of the mixture 
• Absorbance is going to be equal to A=xe+ye
• (e)=epsilon

the relationship between the electrons in the excited states and those in the ground state. Thus the higher the B.D the more atoms in the excited state and vice versa.

• blue shift ( n to pi*)
• happens with polar solvents

red-shift (pi to pi*)

substitute that is attached to a chromophore and usually increases the lambda maximum