C a lib ratio n o f R a m an S p ectro m eter In stru m en t R esp on se

F u n ctio n w ith L u m in escen ce S ta n d a rd s: A n U p d a te

K R IS T IN J. F R O S T an d R IC H A R D L . M C C R E E R Y *
D ep art m en t of Chem istry, T he O hio S tate U niversity, 1 00 W . 1 8th A venue, C olu m bu s, O hio 4 3210

A n error in a p rev iou sly rep orted p roced u re f or correctin g R am a n con sisten cy o f th eir lu m in escen ce. F ig u re 1 sh o w s th e
sp ect ra f or in stru m en t resp o n se w a s corrected , a n d t h en th e a p - un co rrected em ission spectra of sev en 2 3 2 in. ® lters
p roach w as t ested ag ain st rep o rt ed v alu es o f R a m an cross se ctio n s. ob tain ed o n a C hro m ex 2 0 00 sp ectro m eter u p on illu m i-
Th e m et h od u se s lum inesc en t st an d ard s w ith k n o w n em ission
nation b y a 7 8 5 n m laser. T h e ph o tostab ility o f th e K op p
cu rves o f in ten sit y v s. R a m a n sh ift , ex p ressed in p o lyn o m ial fo rm .
A ft er acq u isition o f a n o b se rved em issio n cu rv e f ro m th e lu m in es-
glass w as ex am in ed b y m on itoring the lu m in escence at
cen t stan d ard , t h e co rrection of o b se rved R a m an sp ectra is au to - 16 0 0 cm 2 1 vs. tim e after ex p osu re o f a p ristin e sp o t to
m at ic. A g reem en t o f corrected p ea k a rea s w ith th o se calcu lat ed th e laser. T h e d ecay o f in ten sity rep o rted p rev iou sly 1 o c-
from literatu re cro ss se ctio n s is 5± 2 0 % . T h is co rresp o n d en ce is ap - curred in tw o seg m en ts, a fast perio d u p on in itial ex po -
p roxim ately a s go o d a s t h e a greem en t b etw een d ifferen t rep o rted sure and a m uch slo w er d ecay after ab o ut 5 m in. F or 5 0
values, an d m u ch b et ter t h an t h at o b se rv ed fo r u n correct ed sp ect ra. m W of laser p o w er focu sed to a ; 5 0 m m circu lar sp o t,
D u e t o va ria tio n s in th e lu m inesc en ce o f t h e m a t eria ls, it is lik ely th e fast slo pe w as 9 % m in an d th e slo w w as 0 .0 8% /m in.
th a t t h ese o r sim ila r R a m an in ten sit y sta n d ard s w ill b e calib ra ted F o r a ; 5 0 3 2 0 00 m m lin e fo cu s and 50 m W, th e in itial
b y th e m an u fa ct u rer o r a n in d ep en d en t a gen cy .
slo p e w as 3 % /m in fo llo w ed b y 0.09 % /m in . O v erall, the
In dex H ead ings: R am a n ; In ten sity ca lib rat ion ; In t en si ty stan d ard s;
lu m in escence at 1 60 0 cm 2 1 d ecreased b y 7 ±1 3% d u rin g
In st ru m en t resp on se fu n ction .
th e ® rst 6 m in and an ad dition al 7 % o v er the n ext 1 00
m in . A s no ted p rev io usly, th e em issio n v s. w av elen g th
IN T R O D U C T IO N cur v e sh ap e ch ang es o n ly slig h tly w ith ex p osu re tim e.
F o r ex am p le, th e ratio o f the em ission at 50 0 cm 2 1 to that
In a recen t rep o rt 1 , w e p resen ted an in ten sity calib ra- at 2 50 0 cm 2 1 v aries by less than 5 % o ver 2 h fo r a spo t
tio n pro ced u re fo r R am an sp ectro m eters based o n lu m i- fo cu s, ev en th o ug h th e total in tensity d ecreased b y 20 % .
nescen t stan dard s. T h e stan d ard em its a co n tin u um of In o rder to co n v ert th e ob ser ved ou tp ut of th e stan -
lig h t o ver th e R am an sh ift rang e o f 0 ±3 50 0 cm 2 1 w h en dard s sh ow n in F ig. 1 to th e real o utp u t in term s o f p ho -
illu m in ated b y th e laser u sed in th e sp ectrom eter. P ro v id- to n /s p er w aven u m b er of R am an sh ift, th e o utp ut o f a
ed th at the em issio n spectrum of the stand ard is k n ow n , stan d ard tu ng sten so urce m u st be k n o w n in the sam e
th e in stru m en t respo n se fu n ctio n m ay be d eterm ined fro m un its. T h e b u lb m an ufacturer’ s o u tpu t cu r v e of w atts/cm 2
a sp ectru m of th e stan d ard acq uired u n der th e sam e co n -
nm m u st b e div ided b y hn , then m ultiplied b y l 2 (w h ere
dition s as th e R am an sp ectra to b e calib rated . T h e stan-
l is th e em issio n w av elen g th ) w ith th e resu lt ex p ressed
dard an d sam p le ex perience the sam e o p tical g eo m etr y,
in un its of p h oto n s/s/cm 2 /(cm 2 1 ). T he facto r o f l 2 w as
laser p o w er, etc., an d th e correctio n is easily im plem en ted
neg lected in th e prev io u s rep o rt, 1 resu ltin g in an erro r in
in the spectrom eter or d ata analy sis softw are. In p ractice,
th e lu m in escen t in ten sity an d th e p o lyn o m ials u sed to
corrected spectra m ay b e acq u ired rou tinely after a sin g le
describe its sh ap e. W ith th e u se o f this corrected em issio n
calib ration sp ectrum o f th e lu m inescen t stan d ard . In p rin -
cur v e fo r th e tu n gsten b u lb as a stan d ard , the real em is-
cip le, su ch stan d ard s co u ld b e so ld co m m ercially alon g
sio n cu r v e o f th e K o p p g lass as a fu nction o f R am an shift
w ith a p o lyn o m ial th at d escrib es th eir em issio n in ten sity
relativ e to 7 8 5 nm w as determ in ed b y E q . 1 0 of R ef. 1 ,
as a fu n ctio n of R am an sh ift relativ e to a giv en laser
th en no rm alized to a m ax im u m inten sity o f 1.0. A d eq uate
w av elen g th.
In the in itial p u blicatio n , a system atic erro r occu rred po ly no m ial ® ts to th ese cu r v es w ere o b tain ed b y extrap-
in th e p o ly n o m ials fo r 51 4 .5 an d 78 5 n m stan d ard s, re- olating th e end s o f the cu r ves to 2 50 0 an d 1 4 0 0 0 cm 2 1 ,
lated to the tran sfo rm ation o f th e ou tpu t o f a tun g sten th en least-squ ares ® ttin g w ith a sixth -o rd er po ly no m ial.
em ission stand ard from a n ano m eter to w aven u m b er axis. T h e co rrected p oly n om ials fo r K op p sam ple # 1 an d fo r
In th is b rief rep o rt, w e w ill p ro vid e corrected p oly no - cou m arin 54 0 a are listed in Ta b le I. To test th e rep ro -
m ials, an d also rep o rt som e n ew ob ser vation s ab o u t th e du cibility o f the ® ttin g p ro ced ure, ® v e sets o f in dep en-
rep ro d u cib ility and stability o f the stan d ard s. In ad d itio n , den t p o ly n om ial coef® cien ts w ere d eterm ined for ® ve d if-
com parison of corrected sp ectra w ith literatu re v alu es o f ferent K o p p sam ples (n u m b ers 3±7 in F ig . 1 ). T he em is-
R am an cro ss sectio ns are m ade to assess calibratio n ac- sio n cu r v es calcu lated fro m th ese cu r v es exh ib ited rela-
curacy. tiv e stan dard d ev iation s of 5 .3 % at 1 00 0 cm 2 1 , 3 .5 % at
20 0 0 cm 2 1 , and 1.4 % at 30 0 0 cm 2 1 .
E X P E R IM E N T A L W ith the co rrected p oly no m ials in han d , o b ser v ed R a-
S ev eral sam p les o f K op p ty pe 2 4 12 ® lter g lass w ere m an spectra w ere co rrected b y usin g E q . 1 1 o f R ef. 1 .
ob tain ed fro m G ray G lass C o . (Jam aica, N Y ) to evalu ate T h e stand ard em issio n cu r ve calcu lated from th e p oly -
no m ial w as m ultiplied by th e ratio of the o b ser v ed sam -
Received 3 0 M ay 1 99 8; accepted 24 A u gust 199 8. ple inten sity o v er th e o b ser v ed stan d ard in tensity. T he
* A uthor to w h om co rr espo nd en ce sh o uld be sen t. correction w as im p lem ented auto m atically w ith A rray

0003-702 8 / 98 / 5212 -1 614$2.0 0 / 0

1614 Volume 52, Number 12, 1998 q 1998 S ociet y for A pplie d S pectros copy APPLIED SPECTROSCOPY
F IG . 1. Raw em ission cu r ves f or se v en sam ples o f K o pp 2412 ® lter glass, o btained on a Ch ro m ex 2050 sp ectrom eter w ith 50 m W of 7 85 nm
lase r lig ht. S am ples 3 ±7 w er e fr om the sa m e batch o f glass, w hile 1 an d 2 w ere purchase d se par ately. In tensity ax is is p hotoelectron s co llected b y
a su per pixel resu lting fr om f u ll- height b inning, d ivided by integ ration tim e and lase r pow er m easu r ed at the sa m p le.

B asic in th e G R A M S t so ftw are p ack ag e an d a d isk ® le 7 85 n m b y the facto r n Å O (n Å O 2 n Å j) 3 , w h ere n Å O is th e laser

co ntainin g th e app ro priate po lyn o m ial co ef® cien ts fro m freq u en cy an d n Å j is the R am an sh ift for a g iven peak .
Ta ble I. In p ractice, th e u ser n eed on ly o btain a sp ectru m T h is factor is ap p ro p riate for p ho to n cou n tin g d etectors,
o f th e stan dard (K o pp g lass o r co u m arin so lutio n) b y us- rath er than th e m ore co m m on n 4 factor app rop riate w hen
ing the sam e co n d itio ns as tho se for the sam ple. S p ectra inten sity is m easu red in w atts in stead o f p h oto ns/s. 5
co rrected w ith K o p p g lass are sho w n in F ig. 2 fo r re- S ch roÈ tter and K loÈ ck n er’ s g as-ph ase v alu es in Ta ble 4.4
ag en t-grad e liq u id m ethy lene ch loride, ch loro fo rm , b en - o f R ef. 4 w ere av erag ed, ad ju sted by n Å O (n Å O 2 n Å j ) 3 , then
zene, aceto nitrile, and cyclo hex an e in a 1 cm cuv ette. m u ltip lied b y th e liq uid /gas ratio s o f Ta b le 4 .6 .
N um b ers acco m p an yin g p eak s are p eak areas determ in ed ``D ilor’ ’ refers to spectra o btained w ith a D ilor X -Y
fro m th e G R A M S t ``cu r v e® t’ ’ fun ctio n w ith the u se o f sp ectro m eter ``m acro ’ ’ ch am b er w ith a 3 0 0 lin e/m m g rat-
a Vo ig t lin e pro ® le, 2 an d in clu d ing peak sho u ld ers as in - ing in th e 2 50 m m fo cal leng th ``secon d ’ ’ sp ectrog raph
d icated . T he areas are n o rm alized to th at of a p rom inen t an d an 8 0 0 3 2 0 00 fro nt-illu m in ated charg e-co up led d e-
p eak fo r each sam ple, an d co rresp o nd to th e ``av erag e’ ’ v ice (C C D ) co oled to 2 1 4 0 8 C . T h is sy stem w as n or-
v alu es in Ta b le II. m ally used w ith a 7 8 5 n m T i : sap p hire laser, b ut o cca-
T here is sig ni® can t v ariation in pu b lish ed R am an sio nally w as o p erated at 51 4 .5 n m w ith an 18 0 0 line/n m
cross sectio n s, du e in p art to u ncertain ties in p eak inte- g rating in a 6 0 0 m m sp ectog rap h . T h e stan dard tu n gsten
g ration lim its and a h ost of ex p erim en tal v ariab les. M o st b ulb w as p laced 1 m eter fro m the sam p le p osition , an d
o f th e v alu es used h ere are liq u id-p hase d ifferen tial R a- its lig h t w as d iffused w ith a K im w ip e p laced at the sam -
m an cro ss sectio ns (d s /d V ) fro m eith er N estor an d L ip - p le p osition . T h e sp ectro m eter w as carefu lly sh ield ed to
p in co tt 3 o r S ch roÈ tter and K loÈ ck n er.4 N esto r’ s v alu es re- av oid stray ligh t fro m an y p o in t o th er th an the slit im age
p orted fo r 4 8 8 nm ex citatio n w ere ad ju sted to 5 14 .5 or at the sam p le. T he K o pp stan dard sp ectru m w as o b tain ed
w ith the sam e apparatus, w ith illum ination by a T i:sapphire
T A B LE I. P oly n o m ial co ef ® cien t s f or int en sity st a n d a rd s, n orm al- laser tu n ed to 7 8 5 n m w ith th e aid o f a sm all m o no ch ro -
ized to m a xim u m int en sity. m ato r. ``C h rom ex ’ ’ refers to a C h ro m ex 2 0 00 /2 05 0 m ul-
C o um ar in 54 0 a K o pp 24 1 2 #1 tich an nel spectro m eter w ith a 1 0 24 3 25 6 E E V fron t-
R am an sh ift a (5 1 4 .5 n m ) (7 8 5 nm ) illu m in ated d eep -d epletion ch arg e-co u pled d evice at 2 90
(D n Å )0 0.2 7 01 196 43 1 0.0 1 5647
8 C an d an S D L 85 3 0 laser. F o r b oth th e D ilor an d C h ro-
(D n Å )1 1.5 7 43 416 71 6e-3 6.2 8 4845 e-5 m ex system s, a ho lo grap hic b and reject ® lter p receded a
(D nÅ ) 2
2 1.0 9 57 287 53 4e-6 2 1.5 1 5732 e-8 sin gle spectrog rap h , an d b o th C C D s w ere bin n ed v erti-
(D n Å )3 2.5 6 81 273 90 9e-1 0 8.5 6 4479 e-1 1 cally alo n g th eir fu ll h eig h t.
(D n Å )4 2 2.0 5 94 831 95 5e-1 4 2 9.4 7 2784 e-1 5
(D n Å )5 1.5 9 4599 e-1 8
(D n Å )6 2 1.3 7 5663 e-2 1 R E S U L T S A N D D IS C U S S IO N
a
In w avenum b ers r elative to indicated lase r. S tandard em ission cu r ve
(w ith m ax im um equ al to 1.0 arb itrar y u nits) is r eco n str ucted fr om the
W e rep orted prev io u sly th at th e K op p 2 4 12 g lass
co ef® cients, an d the R am an sh ifts (relative to 51 4.5 o r 78 5 nm ) are sh ow ed g oo d u niform ity o ver 2 8 sp o ts o n th e sam e sam -
raised to the ind icated p ow ers. p le, w ith a 1 % v ariation o f the inten sity ratio at 52 6 and

APPLIED SPECTROSCOPY 1615

 24 1 2 g lass is con v enien t an d has m ost o f th e desired
lu m in escent p ro p erties, b ut rep lacem en t w ith a m ore ph o -
to stable m aterial is still a d esirab le go al. T he co um arin
54 0 stan dard fo r 5 14 .5 n m excitatio n ap p ears stab le ov er
m o n th s o f sh elf life, b ut its em ission m agn itu d e d ep en d s
on an accu rate co n cen tratio n. A s an in dication of th e re-
pro du cibility o f th e 24 1 2 g lass em issio n d u rin g d aily u se
ov er an ex ten ded p erio d, the ratio o f the lum in escen t in-
ten sity at 20 0 0 cm 2 1 to th at at 8 0 0 cm 2 1 had a relativ e
stan d ard d ev iation (R S D ) o f 2.1 % for 18 m easurem en ts
cov erin g a 6 4 day p erio d. T h is p erio d in clud ed a m o di-
® catio n o f th e co llection op tics after tw o w eek s. F o r
tw elve m easu rem en ts o v er o ne m o n th w hen the op tics
w ere un altered , th e ab so lute in ten sities at 80 0 an d 2 0 00
cm 2 1 v aried b y 7 .2 % an d 6 .7 % , resp ectiv ely, w h ile th e
ratio had an R S D of 0.8% .
A s no ted in th e E x perim en tal sectio n , th e p o lyn o m ial
used to exp ress inten sity as a fu n ctio n o f R am an sh ift
w as in creased from fo urth to six th ord er fo r th e 7 85 n m
stan d ard , and the end s o f the raw em ission cu r v e w ere
extrap o lated b efo re th e ® ttin g pro ced u re. T his p rocess
avo ided so m e ® tting aberratio ns n ear 0 an d 3 5 0 0 cm 2 1 ,
and b etter acco m m od ated a sm all feature n ear th e b and
gap of th e C d Te in th e K o pp g lass.
Tab le II lists p eak areas calculated fro m p ub lish ed
cro ss sectio n s, an d th ose o b ser v ed w ith the D ilo r an d
C h rom ex sp ectrom eters, th en co rrected w ith th e lu m in es-
cen t stand ards an d p oly n om ials. F o r th e literature v alues
at 5 15 and 78 5 n m an d b o th sp ectrom eters, th e peak areas
w ere n orm alized to a pro m in ent p eak, so tabu lated v alu es
do n o t in dicate relativ e spectro m eter ef® ciency. E ach re-
petitiv e d eterm inatio n (in d icated b y N 5 6 , fo r ex am p le)
in v o lv ed acq u isition of b o th sam p le an d stand ard. T h e
peak in teg ratio n lim its in dicated in Ta b le II w ere ch osen
F IG . 2. C or rected sp ectra f or ® v e com m on liqu ids, obtained at 785 to be w id e eno u g h to en sure th at a neg lig ib le ( , 1 % )
nm . T he in tegratio n rang e fo r each p eak is sh o w n by th e h orizon tal
bars, and th e nu m erical values are the p eak areas r elative to a pr om in ent
chan g e in area o ccu rred if th ey w ere w id en ed fu rth er.
band. T hese ar eas are the sa m e as th o se in th e last colum n of Table I I. R elativ e stand ard d eviation s fo r a giv en n orm alized peak
A ll sp ectra w ere o btained o n a C hro m ex 2050 sp ectrom eter, sa m p ling area are g en erally in the rang e of 1 ±5 % , bu t w ere o cca-
thro ugh th e si d e of a q uar tz cuvette. sio n ally as hig h as 8 ±2 0 % . T h e co m bin atio n o f all of th e
curren t d eterm in ation s o n bo th sp ectrom eters exh ib ited
an R S D of 5±1 4% .
15 5 3 cm 2 1 . 1 H ow ev er, F ig . 1 rev eals th at d ifferen t batch es If the results from th e p revio u s p aper 1 are recalcu lated
of 24 1 2 g lass h ave d ifferen t em issio n cu r v es. F iv e sep - w ith the correct co nv ersio n o f th e tu n gsten sou rce o u tpu t,
arate 2 3 2 in. sam ples bo u g ht at o nce, an d p resum ably th e v alues are clo se to th o se rep o rted in Ta ble II. T he
fro m th e sam e fab ricatio n b atch, hav e qu ite sim ilar em is- 29 8 8/7 0 2 area ratio fo r C H 2 C l 2 determ in ed prev io u sly at
sio n cu r ves, b ut d ifferen ces b etw een b atch es w ere so m e- 78 5 nm w ith K op p glass b ecom es 0 .6 3 , and the sam e
tim es larg e. A t least for the 2 4 12 m aterial, a n ew p o ly - valu e fo r 5 14 .5 n m an d th e cou m arin stan dard beco m es
no m ial w ill need to be determ in ed fo r each sam ple o r at 0.84 . T h ese co m pare w ell w ith th e cu rrent o bser v ed ra-
least each b atch. If stand ards su ch as th e K op p g lass b e- tio s of 0 .6 6 an d 0 .8 3. F o r th e 22 5 4/9 1 9 ratio o f aceto-
com e w id ely u sed, it is lik ely that each stand ard sam p le nitrile, the prev io u s valu es fo r 7 8 5 an d 5 14 .5 n m correct
w ill b e calib rated b y th e m anu factu rer, as is cu rren tly th e to 3 .3 9 and 4 .1 0 , co m p ared to the current valu es of 3 .3 1
practice for re¯ ectan ce an d ¯ u o rescen ce stan d ard s. and 3 .8 6 . S o , fo r th ree sp ectro m eters an d tw o laser w av e-
T h e p h oto lab ility o f th e 2 4 12 g lass w as n oted earlier len g th s, th e co rrected ex perim en tal peak area ratio s ag ree
and has m in o r effects o n em issio n cu r ve sh ap e an d sub - to 1 0% o r less.
sequ en tly d eterm in ed p eak area ratio s. It w ill cau se erro rs T h e ag reem en t b etw een p eak area ratios calcu lated
w h en on e is com paring th e relative scatterin g o f d ifferen t fro m literatu re v alu es an d tho se o bser v ed h ere v aries
sam p les, ho w ever, o r w h en d eterm inin g ab so lute rath er fro m a few p ercen t (e.g., cy cloh ex an e 12 6 7 , air 2 33 1 ,
th an relative cro ss sectio n s. A s n o ted earlier, d egrad atio n C H C l 3 2 60 an d 3 6 4) to ; 20 % . In som e cases, su ch as
of th e 2 4 12 glass em issio n d epen d s on laser p o w er an d th e b enzen e 30 6 0 b an d , th e literatu re v alu es are in sig -
exp o sure tim e, b ut w as less th an 1 0 % fo r th e few m in u tes ni® can t disag reem en t, exh ibiting . 50 % variatio n . It is
of ex po su re in a ty pical calib ration . W e w ere no t ab le to no t ou r p u rp o se to critically ev alu ate rep orted cross sec-
lo cate a m aterial w ith stab le lu m in escen ce co v erin g all tio n s, b u t cu rrently availab le techn iqu es and stan d ard s re-
35 0 0 cm 2 1 o f R am an sh ift relativ e to 7 8 5 n m . T h e K o pp po rted h ere app ear to lim it th e accu racy o f relative R a-

1616 Volume 52, Number 12, 1998

T A B LE II. P red ict ed a n d co rrected p ea k areas, 7 85 n m excitat ion ( b rack et s ind icate 514.5 excita tion ).
O bse r ved, then corr ected w ith
obse r ved intensity standar d
S am ple
(all pur e liqu ids) L iter ature C h ro m ex D ilor A v erage a
C H 2 C l2
288 cm 2 1
( 225±3 6 0 cm 2 1 ) b 0.5 8 c 0.4 7 6 0.0 2 ( N 5 12 ) d 0 .4 9 6 0.0 4 (N 5 4) 0.4 8 6 0 .0 3 (N 5 16 )
702 cm 2 1
( 600 ±8 50 ) 1.0 0 1 .0 0 1.0 0
2988 cm 2 1 0.5 8 c 0.6 8 6 0.0 5 ( N 5 13 ) 0 .5 9 6 0.0 4 (N 5 4 ) 0.6 6 6 0 .0 6 (N 5 17 )
( 2900Ð 31 50 ) [0 .7 4] c [ 0 .9 9 6 0.1 9 (N 5 3 )] [ 0.8 0 6 0.0 9 (N 5 15)] [ 0.8 3 6 0.1 2 (N 5 1 8) ]
C H C l3
260 cm 2 1
( 205±4 70 ) b 1.1 2 c , 1 .0 2 e 0.9 8 6 0.0 1 ( N 5 6) 1 .0 3 6 0.0 3 (N 5 5) 1.0 0 6 0 .0 3 (N 5 11 )
364
( 205±4 70 ) b 1.1 3 c , 1 .0 3 e 0.9 5 6 0.0 1 ( N 5 6) 0 .9 9 6 0.0 3 (N 5 5) 0.9 7 6 0 .0 3 (N 5 11 )
666
( 550 ±9 00 ) 1.0 0 1 .0 0 1.0 0
758
( 550 ±9 00 ) 0.5 6 c , 0 .6 2 e 0.4 5 6 0.0 2 ( N 5 6) 0 .5 6 6 0.0 5 (N 5 5) 0.5 0 6 0 .0 7 (N 5 11 )
3021
( 2920 ±31 20 ) 0.4 2 c , 0 .4 8 e 0.5 1 6 0.0 2 ( N 5 6) 0 .4 1 6 0.0 6 (N 5 5) 0.4 7 6 0 .0 6 (N 5 11 )
B enzene
992
( 900 ±1 10 0) 1.0 0 1 .0 0 1.0 0
3060 0.8 0 c , 0 .9 2 e , 1.2 6 f 0.9 1 6 0.0 3 ( N 5 6) 0 .8 3 6 0.0 3 (N 5 8 ) 0.8 7 6 0 .0 5 (N 5 14 )
( 2960 ±31 60 ) [ 0.9 9 c , 1.1 7 e , 1.4 8 h ] [ 1 .1 2 6 0.0 4 (N 5 4 )] [ 1.0 2 6 0.1 8 (N 5 8)] [ 1.0 5 6 0.1 6 (N 5 1 2) ]
A cetonitrile
919 cm 2 1
( 825±1 0 25 ) 1.0 0 1 .0 0
2254 3.1 9 g , 2.8 8 c 3 .3 1 (N 5 2)
( 2150 ±24 00 ) [4 .0 f , 3.3 b ] [ 3.8 6 (N 5 2)]
2943 5.8 3 c 7 .7 9 (N 5 2)
( 2800 ±31 50 ) [7 .2 3] c [ 9.7 1 (N 5 2)]
C yclohexan e
801
( 700 ±9 00 ) 1.0 0 1 .0 0 1.0 0
1028
( 925±1 1 25 ) 0.5 8 c 0.6 2 6 0.0 3 ( N 5 7) 0 .6 4 6 0.0 1 (N 5 4) 0.6 3 6 0 .0 3 (N 5 11 )
1267
( 1180 ±13 15 ) 0.4 9 c 0.5 1 6 0.0 2 ( N 5 7) 0 .5 3 6 0.0 2 (N 5 4) 0.5 2 6 0 .0 2 (N 5 11 )
1444
( 1380 ±15 25 ) 0.6 4 c 0.6 3 6 0.0 3 ( N 5 7) 0 .6 7 6 0.0 4 (N 5 4) 0.6 5 6 0 .0 4 (N 5 11 )
A ll C H
( 2587±3 06 8) 6.5 0 c 7.1 7 6 0.7 7 ( N 5 7) 7 .7 4 6 0.6 8 (N 5 4) 7.3 8 6 0 .7 6 (N 5 11 )
A ir
1555 (O 2 )
( 1450 ±16 50 ) [ 1 .0 0]
2331 (N 2 )
( 2225±2 42 5) [ 3 .2 6] i [3 .2 2 6 0.0 4 (N 5 3 )] j
a
A verage o f all d eterm inations o n D ilo r and C h ro m ex sp ectrom eter s. D oes not include literatur e v alu es.
b
In teg ration r ang e f o r peak area. T h e C H Cl 3 26 0 and 36 4 cm 2 1 band s w ere integr ated as tw o bands w ith in the 205 ±4 70 cm 2 1
rang e, an d the 6 66
an d 758 cm 2 1 b and s w er e integr ated as tw o bands w ithin the 550 ±9 0 0 cm 2 1 r ang e.
c
Calculated fr om R ef. 3 as desc r ibed in E x perim en tal se ction.
d
S tated as m ean 6 stan dard deviation. N 5 n um ber of sp ectra an alyzed .
e
Calculated fr om R ef. 4 , as d esc r ibed in E x p erim en tal se ction .
f
C alculated fr om R ef . 6 b y adjustin g repor ted 51 4.5 nm cro ss se ctions by n Å o (n Å o 2 n Å j ) 3 .
g
C alculated by usi ng `` A’ ’ ter m par am eters an d E q . 11 o f R ef. 5.
h
R ep orted in R ef. 6.
i
C alculated fr o m R ef. 4 f o r 2 1 % O 2 , 78% N 2 .
j
F or Ch ro m ex 2 50 sp ectro graph w ith custom 1 80 8 collection op tics.

m an inten sities to ap p ro x im ately 1 0 ±2 0 % . T h e N ation al w ith w av eleng th o v er the co m m o n R am an sh ift rang e,

Institute o f S tan d ard s an d Te ch n o lo g y is cu rrently dev el- an d v er y larg e d isto rtio n s o f relativ e p eak in tensities are
o pin g lu m in escence stan d ard s fo r R am an in tensity cali- likely for u n co rrected spectra. F o r ex am p le, th e ratio o f
b ration th at sh o uld su b stan tially im p ro ve accu racy. 7 the 3 06 0 /9 9 2 p eak area for u nco rrected spectra o f ben -
N ev erth eless, reliab le 10 ±20 % v ariatio n is far less zene at 7 8 5 n m d iffers b y a facto r o f 4 betw een the D ilor
than th at ob ser ved in u nco rrected sp ectra. P articularly an d C h rom ex sp ectrom eters, an d differs fro m th e co r-
w ith red lasers, th e C C D resp o nse cur v e v aries rap id ly rected (an d literatu re) v alu es b y a factor o f ab ou t 5 0 .

APPLIED SPECTROSCOPY 1617

O v erall, th e m ain adv an tag e o f lu m in escen t stan d ard s fo r H urley f or m any u se fu l discussio ns. T his w o rk w as su pported by the
N S F A nalytical and S ur f ace C hem istr y D ivisio n.
correcting R am an sp ectra is the ease and accu racy of th eir
use, p lus th e p recise d up licatio n o f excitatio n co nd itio n s
1. K . G . R ay and R . L . M cC r eer y, A p pl. S p ectrosc . 5 1 , 108 (1 9 97 ).
and geo m etr y for b o th stan d ard and sam ple. W ith suitab le 2. U se rs G uide, G R A M S /3 2 Ver sion 4.0 , ( G alactic S ystem s, S alem ,
lu m in escent stan d ard s available, th e correctio n o f R am an N ew H am p sh ire, 1 996), pp. 2 44 ±248.
spectra fo r instrum en t resp o n se is suf® cien tly straig h tfo r- 3. J. R . N estor and E . R . L ipp incott, J. R am an S p ectro sc . 1, 305 ( 1 97 3) .
w ard to be used o n a ro utin e basis, in a w id e ran g e o f 4. H . W. S chr oÈ tter an d M . W. K loÈ ck ner, in T opics in C urrent P hysics,
Vo l. II , A . Web er, E d. (S pringer±Ve r lag, N ew Yo rk , 19 79), C hap. 4 .
app lication s. 5. J. M . R ud ik, C . R . Jo hnso n, and S . A . A sh er, J. Chem . P hy s. 8 2 ,
1732 (1 9 85).
A CK N O W L E D G M E N T S 6. K . T. S ch om ak er, J. K . D elan ey, and P. M . C ham p ion, J. C hem . P hy s.
85, 4240 (1 9 86 ).
T he au thor s thank L aw r ence R obins at N I S T fo r poin ting ou t the 7. E d gar E tz an d S teven Ch oquette, N ational I nstitu te of S tan d ar d s and
erro r in th e tung sten b u lb em ission cu r ve, an d K enn eth Ray and B elind a Techn ology, private co m m unication.

1618 Volume 52, Number 12, 1998