INSTRUMENTATION
tional frequency directly. Further work using the resonance fluorescence technique with photographic recording showed another electronic state of CuO lying about 4000 c m - 1 above the ground state. Thus it was possible to determine the ordering of the three low-lying states of CuO and to determine their vibrational constants. If we trapped CuO in a matrix that was 85% Xe and 15% Kr, we were able to tune the v' = 2 *— v" = 0 absorption, which appeared at 4781Â in pure xenon, onto the 4765Â line of an argonion laser. When the sample was excited with the laser, fluorescence was observed from the v' = 1 and v' = 0 vibrational levels of the upper state. Observation of emission from the v' = 1 level leads one to the surprising conclusion that the vibrational lifetime of the upper state must be quite long—i.e.,
CuO can undergo about 10B vibrations in a solid matrix without being completely vibrationally relaxed. The analytical applications of matrix isolation spectroscopy are beginning to be explored by Rochkind and coworkers. It has been shown to be useful for the analysis of gas mixtures and isotopically substituted compounds. New sample preparation techniques could widen its usefulness. For example, a focused laser could be used to vaporize a refractory sample and the vapors trapped in a rare gas matrix for analysis. Laser-excited fluorescence, of either gaseous or matrix isolated compounds, could be developed into a highly specific analytical method, since only a compound which has an absorption overlapping the laser line will fluoresce. Laser-excited fluorescence would be quite sensitive as well. The very high intensities possible from laser excitation sources make it possible to detect fluorescence from samples in the range of 10~ 9 mole or smaller. Analysis of air pollutants is a possible application of
laser excited fluorescence now that lasers exist that can excite into intense absorptions of N 0 2 , S0 2 , and 0 3 , as well as many unsaturated hydrocarbons. Combining the techniques of laser excited fluorescence and matrix isolation has been useful or the study of molecular spectra. We are currently working on extending this technique to other complex molecular spectra and to a direct measurement of the vibrational lifetimes of trapped molecules. Laser excited fluorescence of matrix isolated or gas phase samples will hopefully prove equally useful in solving analytical problems. References
Gas Phase Resonance Fluorescence; W. J. Tango, J. K. Link, and R. N. Zare, / . Chem. Phys., 49, 4264 (1968). Matrix Isolation Spectra ; J. S. Shirk and A. M. Bass, J. Chem. Phys., 49, 5156 (1968) ; M. M. Rochkind, ANAL. CHEM.,
40, 762 (1968) ; A paper, "The Absorption and Laser Excited Fluorescence Spectrum of Matrix Isolated CuO," by J. S. Shirk and A. M. Bass has been submitted to J. Chem. Phys.
COMMENTARY by Ralph H. Müller
T^HIS
CONTRIBUTION of
Drs. Shirk
-*- and Bass adds to the list of interesting and important articles which have appeared in this column during 1969. The techniques for producing matrix-isolated molecules suitable for laser-excited fluorescence are clearly explained, as well as indicating numerous analytical applications. I t seems obvious that what the authors have done is more than adequate to demonstrate the importance of the new techniques.
"Because It Is There" ADVENT of the Apollo XI misT HE sion sets July 20, 1969, as the date
for the greatest technical achievement in history. The accomplishment beggars description and even the vast resources of the English language fall short for suitable adjectives. People throughout the world hailed the event for the simple reason that it was a unique expression of the human spirit. The few sour notes which were heard emanated from regions where few fet106A
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ters are ever sundered, and that was to be expected. People of vision and goodwill shall continue to praise NASA and the three superbly trained astronauts for the execution of the mission, and whatever honors come to Armstrong, Aldrin, and Collins are well deserved. Scientists and technologists will eagerly await the results which accrued from the voyage. Their complete documentation will require years, even though Apollo X I I will be on its way in mid-November to add still more data and knowledge to the subject. We believe it would be in the best public interest if NASA were to publish a detailed account of what is planned for the Apollo XI mission. We say planned rather than accomplished because rarely, if ever, in the history of experimentation has such magnificent agreement between calculated and observed been attained. An article entitled "Instrumentation Aboard LM" [Instrumentation Technology, 16, No. 7, 32 (1969)] presents interesting details of the propulsion, navigation, and computer assimilation of data. A striking feature of the gen-
eral design is the large amount of redundancy which was purposely incorporated, so that reserve systems could be automatically switched in upon failure of any component. The details of telemetry and communications could fill volumes, and they constitute a large fraction of the entire set of operations. The maintenance of intelligible communication over these vast distances was most impressive. That much of the conversation was conducted in pidgin English may well entitle our literary scholars to repeat Professor Morse's query, "What hath God wrought?" C&EN has already outlined the plans for the examination of lunar samples and how these will be studied by scientists all over the world. What was collected was necessarily limited, considering the brief time available and the relatively restricted area of useful operation. Among all scientists, perhaps only the analytical chemists will be worried by that question of "a representative sample." At the time of this writing, the location of the corner reflector for laser
INSTRUMENTATION
beams has been found. If it can be kept "on target" for protracted periods, it can yield data of enormous value. The same is true of the solar wind screen (now back on earth) and the seismograph which, hopefully, will not succumb to the high temperatures. We believe that much could be ac complished if a large number of special instruments with appropriate telemetry could be placed in many locations on the moon. I t is unfortunate that they cannot be parachuted down, but per haps cheap retrojet systems could be designed for the purpose. For the time being, they could be much cheaper than landing men to do the work be cause the job of getting men back is enormous. If the immediate purpose is to get as much information as pos sible per unit cost, it would seem to be a continuing question between manned and unmanned missions. No one doubts the tremendous boost in morale which a manned landing has given to earthbound people, but we have long believed that machines should replace men in routine, repetitive, and exhaust ing tasks. Much nonsense has been spoken or written about the significance of the Apollo X I mission, and most of it is simply a lack of historical perspective. Scientists know, or should know, that the measure of any achievement must be appraised within the framework of the times. The genius of Copernicus, Tycho Brahe, or Kepler was in no wise inferior to present day astrono mers or cosmologists who have vastly better equipment and computational aides. I t detracts not one iota from the credit due NASA and the valiant astronauts to say that a comparison of their voyage with that of Columbus is essentially pointless. One may well ask which was more useful and profit able to mankind. The astonishing suc cess of this mission is proof positive that we knew precisely where we were going, what was there, and that it was bleak, forbidding, inhospitable, and completely unsatisfactory for human habitation. By bringing his own en capsulated environment, man achieved a brief and successful visit. As has been said, Columbus didn't know where he was going when he started, didn't know where he was when he got there, and after another voyage or two, was thrown briefly into a dungeon for his pains. But what did he find? A tropical paradise with lush vegetation, exotic plants and fruits, and an almost inexhaustible source of treasure which
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enabled Spain to loot, plunder, and ex ploit for another century and a half. As it turned out later, he had arrived at the gateway of an entire hemisphere. All this with three tiny vessels, a panicstricken and mutinous crew, in an age of ignorance and superstition, and in times when such ventures were usually construed as an affront to God and His will. Magellan, Vasco da Gama, and others were equally inspired and val iant and accomplished wonders under circumstances which we can hardly ap preciate and are all too prone to forget. A superb technology fits us to do fantastic things whether they are de sirable or not. There is much truth in the slogan, "The difficult we do im mediately—the impossible takes a little longer." Everest was scaled and had to be "because it was there." Does any one doubt that with a few hundred or thousand thermonuclear bombs we would level it to suitable heights to build a city there with four lane high ways for access and with suitably spaced hamburger drive-ins ? We could build a huge subterranean city under the Mohave desert with water piped in from the remote Columbia river. If any water seeped to the surface and permitted wild flowers to flourish, they could easily be blasted off with acetylene torches. We all know of the Italian volcanologist who pointed with pride to the smoldering crater of Vesuvius and said to the American tourist, "Surely you have nothing like this in America." "Right," replied the Yank "but our Niagara Falls could put that darned thing out in five minutes." Shall we hold our breath and keep our fingers crossed lest some enthusiastic technologists decide that it should be done, and then before we know it, all systems will be GO ? Let us continue to explore space with the best scientific resources and, for the time, ignore the dreamers who want to colonize and inhabit it. We have per formed wonders on Earth, but we still don't know too much about managing the place. Those who want no more space exploration but an immediate solution to urban renewal, abatement of pollution, and perfect race relations ig nore one fundamental fact. We have the technology but not the total col lective will and determination to do so. Each of us, to some degree, is greedy, prejudiced, and not quite equal to the sacrifice, labor, goodwill, and vision which is required. It is a problem of the human spirit—the technical prob lems are duck soup !
