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physical 3 - spectroscopy > electronic spectroscopy + IR > Flashcards

electronic spectroscopy + IR Flashcards

1
Q

photoelectron spectroscopy has enough energy to do what

A

enough energy to ionise

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2
Q

what is einsteins equation involving hv

A

planks x frequency =
ionisation energy x kinetic energy

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3
Q

what does hv = Ke + Ie tell us

A

that if we know a photons energy and it’s kinetic energy, we can find it’s ionisation energy

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4
Q

what is the process of photoelectron spectroscopy

A

shining hv on a sample ionised it and causes it to lose an electron

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5
Q

what is hv

A

energy of a photon

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6
Q

what does XPS stand for

A

x-ray photoelectron spectroscopy

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7
Q

what is x-ray photoelectron spectroscopy used for + characteristics

A
  • identifying chemical elements present and their environments
  • quantitative
  • surface selective
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8
Q

ratio of surface to bulk

A

1 : 10^8

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9
Q

electronic spectrum of the H atom emission spec diagram exp

A

promoted electron falls to lower energy level and emits a photon.

light is seen as this occurs.

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10
Q

what is an alpha transition

A

lowest energy transition
the energy level right above the ground state

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11
Q

what is the alpha transition for the lyman series

A

2

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12
Q

what is the alpha transition for the ballet series

A

3

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13
Q

what is the alpha transition of the paschen series

A

4

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14
Q

what is the series limit transition

A

energy when electron falls from infinity to ground state

highest energy transition

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15
Q

what light is lyman

A

UV
level 1

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16
Q

what light is balmer

A

visible light
level 2

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17
Q

what light is paschen

A

infrared light
level 3

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18
Q

what does the series limit correspond to

A

the ionisation energy

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19
Q

from the alpha transmission to the series limit transition, what happens to the energy spaces between then

A

they get smaller
the energy difference is smaller

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20
Q

when light emitted is plotted against energy where does each series go

A

paschen = smallest energy, all lines have the same light intensity

balmer = middle, all lines have the same light intensity

lymann = highest energy, the same light intensity

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21
Q

in hydrogen atom emission spectra, what series had the highest wavelength

A

lymann = shortest
balmer = middle
paschen = longest

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22
Q

what is the rydberg equation for v- aka wavenumber

A

Rh = (1/smaller n2 - 1/larger n2 )

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23
Q

rydberg constant value and units

A

1.097 x 10^5 cm-1

24
Q

what is the n1 aka smallest n value for the different series when finding v- wavenumber using the rhydberg equation

A

lymann = 1
balmer = 2
paschen = 3

these are the lowest energy levels the electron can fall to.

25
Q

what is n2 aka the largest number that an electron can fall from for each series

A

infinity

26
Q

worded rhydberg equation

A

wavenumber = rhydberg constant x (1/ where e- is falling to squared) - (1/ where electron is falling from squared)
in cm-1

27
Q

infinity 2 gives what value

A

0

28
Q

what happens in UV VIS spec

A

absorbance of light or radiation excited electrons from group state to the first excited stage of the compound.

go to the anti binding orbital??

29
Q

isobestic point

A

no intermediates
molecule / state changes to another directly

seen in UVVIS spec

30
Q

IR radiation can do what to molecules

A

cause a shape change
stretch and bend them.

31
Q

when an atom is pulled apart to its max it has what

A

maximum extension
LARGE POTENTIAL ENERGY

32
Q

when an atom is at its normal bond length is has

A

minimum extension
minimum potential energy??

33
Q

r is theeee

A

the bond length

34
Q

what is the harmonic oscillator

A

U shape
shows relationship between potential energy and r (bond length)

35
Q

harmonic oscillator explanation

A

as bond distance increases, potential energy decreases to a trough then increases again

36
Q

we can only oscillate smt atttt

A

particular energies

37
Q

what is oscillation

A

back and fourth rhythmic movements

38
Q

vibrational energy is

A

quantised

39
Q

equation to show how vibrational energy is quantised at energy level V

A

Ev = hw ( v + 1/2)

where v is a quantum number for vibrational level (1,2,3,4)
h is planks constant
w is fundamental frequency (s-1)

40
Q

energy for vibrational level 1

A

E1 = h w (1 + 1/2 )

= 1.5 hw

41
Q

what is hw

A

fundamental frequency

42
Q

when energy is plotted against distance u get a parabola for potential energy. the distance between vibrational levels is

A

hw

43
Q

zero point energy

A

V=0

E0 = hw (0 + 1/2)
= 1/2 hw
this is bc a molecule cannot have 0 vibrational energy

44
Q

change in energy between 2 diff vibrational energy levels

A

Change in E = final - initial values

values = answers to Ev = hw (V + 1/2 )

45
Q

what is w and it’s units

A

fundamental frequency
s-1

46
Q

how can we find the fundamental frequency, w

A

W = 1/2🥧 x 🟫🌳 k/ reduced mass

47
Q

k is the

A

force constant
aka strength or the spring

48
Q

if there’s a larger k value that means there is a larger

A

w value

49
Q

what is reduced mass for a bond between 2 diff molecules // 2 of the same molecules in kg

A

(M1)(M2) / M1 + M2

50
Q

when finding the M1 and M2 what must we do

A

mass of atom / avogadros constant

then apply it to M1 and M2

51
Q

selection rule for IR SPEC

A

gross selection rule

52
Q

what is the gross selection rule

A

in order to interact with infrared radiation, a vibration must have a changing dipole

53
Q

how many independent directions can an atom move in

A

3
along the x, y, z axis

54
Q

total degrees of freedom = 3N

A

where n is the number of atoms.

55
Q

what is the other specific selection rule

A

in a simple harmonic oscillator, the change in V can only be -+1

u cannot jump 2 levels

56
Q
A
57
Q
A

physical 3 - spectroscopy (12 decks)

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