Studies in Molecular Spectra

95 Pages·4.999 MB·English

by  Joyner, Powell A

STUDIES IN MOLECUUE SPEOTM
by
Powell Austin Joyaer
State University of lows
LIBRARY
k dissertation submitted a partial fulfillment of the requirement®
1
for the degree of Doetor of Philosophy* in the Department
of Chemistry in the Graduate College of the
State University of Iowa
February 1961
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T m
ACKKmBMIOTS
The m iter has teem aided by many individuals la thie research
cad itt happy to acknowledge the debt. Special thanks are due to the
following s
To Professor George Sleekier for inspiration and guidance in
thie reeearoh as m il as in other endeavors*
To the Graduate College of the State University of Iowa for
the reeearoh assistant ship*
To the Research Corporation of ihaerloa for funds for the pur*
chase of the spectrograph*
To Dr* B» C* Britton of the Dow Chemical Company for the
sample of vinylidene chloride*
To Dr* !« Dean Mallory who introduced me to the experimental
technique of Raman spectroscopy and contributed valuable suggestions*
To Mr* Paul Harper* University Mechanician* for construction
of the drying columns*
To Mr* H« $♦ BOxraaineker, University Glassblower* for valuable
suggestions and fbr construction of the Raman tubes*
. To Mr* John Thomas and the storeroom staff for their prompt
and willing cooperation in ordering and securing supplies*
table of m m m n
Chapter pegs
Intreduebien * * * • * ♦ * * • * « « • * * . ***
1 1
.S!fa»-'&MIMS 'SUPiDM%a * • » • • • « * » * • « • • %
Purpose of the Investigation* * * * * * * * * 3
II Purification and Handling of Sample* • « • • • * •
6
Vinylldone Chloride * * » * « « # # « « » « • 6
The Vacuum System « * * * « » * « « » « • * •
0
Cleaning the Raman Tube * • * * • # * * * * « 10
Teats for Optical Purity* * * * * * * * * * * 13
Masking the Reman Tube* « « * » « * « * * * * $
1
tit The Spectrograph and Exolt&tion Unit * • • * • • * 10
General Description * » « * « * » « « • * • « 18
Hotoe on the Operation of the Exaltation
Unit* * « • « » ,
* * * » » « * * « * * » * 2 0
I? The Optics of the Raman Tube * » # * * * « * » * • 24
The Position of the Sample Tube and Con**
denser lease* * * • • • • • * * * * « • • « 04
Mirrored Raman Tube « * * 20
« » « « * » * » * 9
V Sample Cooling System and Filters* « • « * * * * • 33
Cooling System* • * » « • « * » • « « » « » » 33
Filters * * * « • » • » « • * • • * * * * * * 38
VI Measurement of Plates* # « « * * • # * » * * • * » 40
Processing* • • * « • * « « « . » • • * » • » 42
Comparator and Dispersion Formula • • • * * « 42
Reference Speotrum* • • * • » • • * » • • « » 42
A Hew Method for Marking Faint Lines for
Measurement « « » * • « » « * * • • • • • * 48
VII Summary of Experimental Conditions * • » • * • • *48
VIII Experimental Results « • « * « • » * « » « » **«@0
lii
Chapter peg®
XX Assigssasats of Vibrational Frequencies of
Vinylidene Chloride » * * * * * . * . * * * < » ® 62
Assignment of Ftandasaanbals » * * * * • » « « @2
Interpretation of Overtones end Combina­
tion Frequencies * # « # » « • « # * « * • 67
X Assignment of the FundMnentoX Frequencies of
1,1 Diohloro 2,2 Difluor© Bthyleno* « • • • » * 76
XX Design for A Self ^Purifying Mm®, Tub## * « • * * 81
XXI Stuaiaary « « « » * * * « * » . * * « * * * * * 0 o84
Bibliography* * * * * * * • * » * * « * * # « * * $S
Biographical Sketch • * » » • « » * « • • « • » • ?
8
It
fflUKJS OF TABI^S
nm* p*g®
I Speotxw of Vingrlidene Chloric « * ». * «. » * $1
It Infre^Eed Spectrum of Vinyl i toe Chloride
{AfW Thompson tod Torkingtou (16)}* * ® * * * •
66
ttt Bymmtvy Properties of Vinyllden® Chloride* * * * * 68
IV The Fundamental Frequencies of CIgCFg, CHgCBrg*
CHDCBrgii tod CDgCErg* * * * * * * * * * * * * * * 60
V the Fimdnjaental Vibrational Frequencies of
Vinylldeae Chloride « * • # • • • ♦ # •• * * * * 8 6
tl Symmtxy Spool©s for Combination end Overtone
Vibration® of the Point 8r<mp Cg^p *• • • « »»«68
til Interpretation of Overtone tod Combination
frequeneito of Tinylidone Chloride# * * * • » • * 74
till Inman end Z$fr*HB d Spectra of CClgCFg* * # • * * * 76
6
£& Fundamental Vlbratioaal Frequencies of COlgCPg# * « 78
TABLE OF FtGDBBS
Figure pag®
1 The Vacuwm Systom « • • « * « . « . . * » * • * » ©
The Loading A^^ombly, t i « < « • * • i » » « « • XX
2
5 Basked Raman tub© * « • • • « • * • « • * • • * * X?
© Optics ©f the tasaan Tub©* * « « « » * « * * • « * $1
5 The Bryl©® Oeftamr * • * • # * * * * * *■ » » * * 34
6 Heating and Cooling Curves* * * » » « * » • • « * 36
T Harking faint Sanaa tines » « * » « . « « • • • « 43
$ Filememb Harking an Argon Line* • * • « * • • » • 43
$ Filament Harking a Eaman Line » » • • * » • « . « 47
10 The Ooometiy of mnyUden© Chloride..........................63
11 Infra-Eed Sand type® Displayed by Fiaylidene
Chloride* « * » , • * * * * * » • • * * * « « •
66
12 Fundamental Frequencies ©f the Vlnyliden®
Hal Idea * * « » .................. * • . * ....................
66
13 Comparison of the Fundamental Frequencies of
O%0%* CCtgCFg, and CHgCClg. . * * * * * . » . 60
14 Diagram of S©If*FurIfying Hasian Tube. * * » • • » 82
16 Photograph of SelMUrifying Raman Tub© • » » . » 83
vl

1
Chapter I
isjfRomJcmG®
fly Raman Effect
At light traverses a substance It may either be absorbed*
transsd ttcd* or scattered* A medium my scatter light by three pro*
cessess Tyndall scattering* which is essentially reflection by par*
tides la the medium* Haylelgh scattering* caused by inhomogeneities
with dimensions comparable to the wave length of light? end by Hie
Raman Effeet* the latter process differs from the other two In that
the scattered li^it staffers a change in wave length* The Raman Effect
was theoretically predicted by Smekal ( ), and first experimentally
1
observed by Rsman and oo-worfeers ( ) in 1928, during Hie coarse of
2
experiments on the scattering of li$it by liquids and solids*
The simplest explanation of the Raman Effect is that a photon
of energy fefj Interacts with a molecule whose state is altered by the
process* and the scattered light emerges with an energy of hvg# Since
energy must he conserved In the process* we have
hwt * * h*g * Eg
or % * Ej, s: h(vx * * )
2
where E^ energy of the initial state of the molecule
5
% energy of the final state of the molecule
5
thus * eg* or as it is more customarily written m 9 corresponds to a
difference in energy levels of the molecule* These differences in
energy ere identified with the vibrational {and/or rotational) states
a
of to molecule* 91m wave length th in of the scattered frequencies Is
to important consideration and Is eharaoteristie of to material to
independent of to eaeiting light* Frequently quo observes those Raman
displacenmnts on either side of to exciting wave length* Those on to
long noire long**1 *id« ere sailed n8tekee lines11, in analogy to Stoke*1
lesr of fluorescence* to those on to other side wAnti-Stokes 11m *n*
In to ease of the Stokes lines, to mole mile effected is raised to a
higher vibrational (and/or rotational) level, to in to case of the
Amti«*Stoke* lines to transition Is from a higher 'vibrational or rota­
tional state to a loser one* Sines, under usual circumstances, to
population of to energy levels above to ground state is relatively
small, to Anti-Stokes lines are much weaker than to corresponding
stokes lines and are usually observed toy for to lowest vibrational
levels* It Is ton possible to obtain information concerning to vibra­
tional states of a molecule by observing its Raraam spectrum*
there is a further feature of importance in the Raman Effeet*
Although to light scattered by a Rayleigh mechanism is highly polarised
(tom observed at right angles), the Raman displacements may exhibit a
wide range of states of polarisation* The state of polarisation of a
Raman line le intimately related with the symmetry of the vibration
to t caused it*
One may ton study the vibrational states of a molecule by
to methods of spectroscopy in the visible region as well as in to
infra-red* However, the information obtained by these two methods is
not entirely to seme, due to a difference in mechanism that gives rise