Engineering Research Institute University of Michigan Ann Arbor Quarterly Report No. 5 on Infrared Studies of Crystals (Period: 15 August 1952 to 15 November 1952) Go Bo B. M. Sutherland Principal Investigator R.T. Wara We Go Simeral Project M957 Signal Corps, Department of the Army Contract DA 36-039 sc-5581 SC Project 152B-0, DA Project 3-99-15-022 Squier Signal Laboratory, Fort Monmouth, N. JNovember 1952

Table of Contents Page Io Purpose of the Research 1 IIo Account of Work Done and Future Program As Barium Titanate 1 B. Mica 1 C. Diamond 3

Quarterly Report Noo 5 on Infrared Studies pf Crystals Io Purpose of the Research See 1st Annual Reporto IIe Account of Work Done and Futre Program:. ~Ql...p. t-. (A) BARIUM MTITANATE ('Mr RO:T Mara): Nothing new to repor here except that work is ender way to obtain the spectra of Te02, IrO2, GeO2, SnO, PbO2, MnO2, V02, and Cr02, all of which have th. same crystal structure as TiO2. (B) M-ICA (-Mr HRo To. Mara): Work -as been.done on the dicahrT'm of c-ertain OH banid-S n muscovite "and.on the spectra of muscovite and phlogopet* in the region between 10 and 33p5. (a) Polarization Studies Pre-liminary: obseration (-:e the -Pi-rt Annual Report) seemed to indicate that.thq. dichroism of the 1,o4. band in musovi-^-te- was muaeh g-reat-er than that of the 2.,8k band, This -oserTvation' is'in-onsis'tent-'with: the asig'ent of' the 2o 8 band as due -only to the OH st"retching'fundamental and the 1,4 band as it's overtone In an -e-ffrt to.clarify this situation, f'urther siitudy was made of the polarization characteristics of- these bands. The earrly polarization work on the 1o4 band was done with a muscovite sample 250(. thick. This resulted in only about 15% absorption at 1,4^, which was not sufficient for accurate quantitative measurement F Polarized spectra of a thicker sample (about 902p) of the same muscovite have been obtained covering the 12:-o5V. regiono Spectra were

taken with twenty settings of the polarizer covering 180~e A plot of the percent transmission (I/Is) vs the angle of polarization was made for the lo4k and 2 2p bandso Using a thin sample (about 2p thick), the same was done for the 2o8k band, The curves indicated that the l1o4, 2.355, 2s45V, and 2,8p bands are polarized in the same direction, with their maximum absorption along the b-axis of the crystal. The 2e2i band exhibited its maximum absorption when the polarizer was oriented along'the aaxis (perpendicular to the b-axis) The directions of the a and b axes (which are in the plane of the mica sheet) were determined by use of a polarizing microscope' For the thick sample (about 902[)O, the fractional transmission I/Io for the 1.a4i band varied from 0O310 to 00650 when plotted against the polarization anglee Defining 8min = In ( X mO a maI Maix nOX v in and the dichroic ratio 9 as 6max 6rnain a value 90 2o72 was obtained for the 1.44 band. When the thin sample (about. 2p) was'used, I/Io for the 2-,-8p band varied from-0o250 to 0585o This gave 9F g 2o61 for the 2o8p bando The values of 4 and pw differby about 4% which is within the expected experimental erroro This result confirmes...the -..assigi.nment of the 1o-4p band as the overtont of — the- band - at 2 —8, p. It -should -be -noted that these valuea are considerably higher than that obtained by Tsuboi for the 2o8p band (vizo 1037)o ==kx Assuming Beert S Law, I Ioe the -absorptioncoefficient, k, at the _peak of the 104p band was- alculated to be 1.05 x 10-3 per microne This value was cheeked by predicting the percent transmission at lo4'for the various thicknesses. The variations from the observed percent transmissions were within experimental error^ The above work was done on the muscovite sample whose spectrum was given in Figo III of the First Annual a2

Report, and whose extended spectrum is given in Figo I (a) of this reporto All polarization work reported here was per'formed on a Perkin-Elmer model 21 double beam instrument equipped with a rock salt prism. (b) Long Wave Length Region The long wave length region has been explored for three mica sampleso The spectrum shown in Fig. I (a) is of a muscovite sample that shows only the free OH band at 2o8p and its overtone at 1.4jx, and no other OH bands (see Fig0 III, First Annual Report)o The muscovite sample used for Figo I (b) exhibits not only the free OH bands, but also hydrogen bonded bands at 3ol1 and 7O05j (see Fig. IV, First Annual Report). Synthetic phlogopite containing no hydroxyl groups was used for Figo I (e)~ It was hoped that by comparing these three spectra an OH deformation frequency could be located in the longer wave length region. It will be observed that the muscovites which exhibit stroup OH bands near 2.o8 also exhibit a band near 410 cml which is absent from the spectrum of synthetic phlogopite which has no OH groups (and no band at 28p.)o4 It is not certain yet whether this correlation is significanto It may be noted, however, that the spectra of two phlogopites which contained varying amounts of OH (Figso II (a) and II (b) of the 4th Quarterly Report) show significantly more absorption in' the region of 410 cm"rCl than the phlogopite containing no OHo The only other important differences between. the three spectra of Fig. I fre that (a) and (b) show a clearly resolved band at 930 cm which only appears as a shoulder in (e) and that (a) and (b) show a band at 800 cm-1 which is absent in (c), A Perkin-Elmer model 21 double beam instrument with a rock salt prism was used to obtain the spectra in the 1-lOj region, and a Perkin-Elmer model 112 double pass spectrometer with a CsBr prism was used for the 10O33s regions FUTURE -PROGRAM: Work till continue on the identification of OHI frequenc ies in the micas and on measurements of their polarization propertieso (C) DIAMOND (bMo. We Go Simeral): The greater portion of the period has been devoted to calculations concerning the loea 3

tions of the maxima in the frequency distribution of diamond. The results are incomplete and will not be presented at this time The following experimental results have been obtained: (1) Neutron Bombardment - Four diamonds have been ex~ posed to a total of 30 hours of irradiation in the Oak Ridge Pile. The infrared classification of the stones ranged from.strong Type I to Type II (see First- Annual Report).e At the endd of the 530 hours of irradiation all four diamonds showed a dark green color by transmitted light. The color of the individual stones appeared to be independent of their Type or their' origina'l oloro No definite effects were found in the infrared spectra of the irr'adiated diamondsa If there was any ihncrease in the intensity of. the Type..I'bands, it'was too small to be clearly separ'ated from the experim"ental v'aria tions. Be Bef6re returniing the diamonds fdor additional bombardment, the absorption spectra in the near ultraviolet and visible will be examinedt (2) Ultimate Carbon Analy si: Samples from thr ee diamonds wee submitted t Car Miroanalytic a Labora tory for i a - measurement. of the total arbon content.' Previous results on diamond dust (see First Annual Report ) indicated'that this procedure would be successful. However, it did not prove possible to oxidize the sr'na1 fragments of diamond at a fast enough rate to mak e a successful analysis" Either the impurities in the dust catalyzed the previous oxidation, or the- state of subdivision. influences the-rate of combusti6on The latter observation seems more plausible. (3) Vacuum Ultravioliet Absorption: Measurements; have been m-ade i' the spectrl regionfrm 1300.to 5000A using a Cario-Sehmidt-ttt spectrograph'. The source of.radiation was a hydrogen discharge.lampe The absorption...spectra of several damonds of vayin... Type all showed complete absorption in the spectral region from 1300A to 2250A. Construction of a new source infor use in obtaining the infrared spectra of diamonds in the 20p region is underway FUTURE PROGRAM: Construction of the above mentioned source will pbe copletedT It has been found that present equipment must be 4

modified before the small diamonds in the Grenville Wells collection (see Quarterly Report NOo 4) can be examined;in the infrared. The necessary modifications are underwayB Samples of highlst purity germanium should be available in the near future* These samples will be examined in the entire infrared spectral region available on our apparatus (1 to 15OV)o The calculations dealing with the correlation of theory and experiment for the infrared spectra of silicon, germanium, and diamond -will be continued. 5

20 Muscovite (Free OH) -- 125p I I I I -2zj C') u) C c (0 Fa) a) I. Muscovite (Free ~ Bonded OH) I I I I I I I I I I "2p -4 2400 1600 600 400 cm Fig. I Spectra o- three rmicas (a) a muscoviite containin\ free OH Nroups, (b) a muscovite containing free and bonded OH groups and (C.)I synthe+ic phlogopite containing no OH groups - for conparison in the lon? wave length region.