Pioneers in Science and Technology Series: William (Bill) Arnold

              

PIONEERS IN SCIENCE AND TECHNOLOGY SERIES

ORAL HISTORY OF WILLIAM (BILL) ARNOLD
Interviewed by Clarence Larson
Filmed by Jane Larson
March 4, 1986
Transcribed by Jordan Reed
 
MR. LARSON: …is a good place to start from.
MR. ARNOLD: I was born in Douglas, Wyoming, in 1904, and my father ran a contracting business and a hardware store. when I was about five or six, he decided he wanted to raise fruit. He sold off his business, we moved to Oregon, near Eugene, where he and a doctor in Douglas, a friend of his, bought a farm and they planted apples, peaches, and prunes and we were in the fruit business. With the exception of time during the World War when my father was in the Army, we stayed on the ranch until 1920, about 1920.
[Break in video] 
MR. ARNOLD: The only course that would fit my program was a course in physiology that was considered a junior course, but if I took that course, that would count. This course was given by a man named Robert Emerson, who had got his degree with Barber, was very well known in photosynthesis. I knew vaguely what photosynthesis was, but that was the way it was started.
MR. LARSON: Oh yes.
MR. ARNOLD: I liked Robert Emerson very much. He was a very nice man to deal with and a good experimenter. He told us about the work that [Otto] Warburg had been doing. Warburg had just shown that it took four quanta to reduce one CO2. And went over all that and he was particularly interested in an experiment that was, had been done first by Brown and Eskom in 1905, I think, some time like that. 
MR. LARSON: Oh yes.
MR. ARNOLD: Warburg had redone this experiment. Now it’s a little hard to explain, but let’s imagine that you look at a field of view, and you have a shutter like an electric fan, but it leaves open, a certain fraction of the time, and leaves it closed a fraction of the time. It’s well known that for your eyes the light goes down strictly to the area you get through if you have a shutter open one fourth the time and closed three fourths the time, that light looks four times dimmer, very accurately it’s proportional to the energy that gets through. When that experiment was tried on plants, it didn’t work that way. 
MR. LARSON: Oh, that’s a very remarkable discovery.
MR. ARNOLD: Yes, and Emerson felt that this was very important. Now he was doing these measurements in a tank that had to be kept a constant temperature and you did monomeric measurements, you know the Warburg manometers…
MR. LARSON: Oh yes, gas measurements. 
MR. ARNOLD: …measured gas and you had to hold the temperature very accurate. It was very difficult to get the optical line in. So I went to the professor and said there was a much simpler way of doing this experiment. You could use sign lighting…
MR. LARSON: Oh yes. 
MR. ARNOLD: Neon signs because the color would be just right for green plants…
MR. LARSON: Yes.
MR. ARNOLD: And they could be turned on and off fast. And they could be made any shape you want. If you made a “U” shaped sign that came down over and up that could be put right under the water, under the vessel, it would be easy as pie and then you control all the time on and off electrically.
MR. LARSON: Oh yes. Wonderfully ingenious approach. 
MR. ARNOLD: This was going to maybe get me in good with the professor…
MR. LARSON: Naturally.
MR. ARNOLD: …and help him out with his experiment. But somewhat to my astonishment, Emerson took the idea to the biology faculty meeting. He said he had this kid that had suggested a very new good way of doing this experiment over and there was money they could put on research. So they said Emerson could go ahead. I was called in the next day and Emerson said that he had money for this experiment now and if I would start and help him with the experiment and get it going, why, I could instead of going to the laboratory class for the course I was taking already in place of another course. 
MR. LARSON: Oh yes.
MR. ARNOLD: Well imagine being an undergraduate and having a research budget. That’s pretty good. 
MR. LARSON: That’s really wonderful.
MR. ARNOLD: So I started on this experiment and I suppose it was luck that this thing worked very well. We got it and we could do the Warburg experiment over as we shortened the time. we got more and more photosynthesis, utterly out of range of the optical effect of spinning the thing in front of your eyes. 
MR. LARSON: Oh yes. 
MR. ARNOLD: Well, to make a long story short, you see we started by changing the length, by playing with the AC circuit, so we went to a condenser discharge. You see, I knew everyone in the Physics Department, people working on these things. So, we simply charged up an electrical condenser and put through the discharge tube a flash of light. 
MR. LARSON: So you would get flashes.
MR. ARNOLD: Yeah, and then you could put them different distances apart and it turned out that this experiment was really a success. 
MR. LARSON: Good.
MR. ARNOLD: Then graduation day came around. I had been writing to observatories to find a place to be a graduate student.
MR. LARSON: Oh yes. 
MR. ARNOLD: But I didn’t find any. Emerson said, “Why not take off a year?” and work with him. So that would be, ’31 I graduated. So I stayed on and we continued these experiments and, now let me get this straight. During that year, I tried to find a place as a graduate student but we went ahead with the experiment, and when we found that you could give a flash of light you see, you change and increase the distances out, you got more and more photosynthesis per flash and it was saturated which meant that you see a chemical reaction was finishing itself up. And the light reaction, if you change the light constantly, it would go up and saturate. It was obvious that if we did both at once, we would have the maximum photosynthesis per flash. If we did that experiment and at the same time measured the chlorophyll compound then we would know how many chlorophyll compounds reduce one CO2.
MR. LARSON: Oh yes.
MR. ARNOLD: Now at that time, there was no doubt in anybody’s mind that it took four quanta to reduce one CO2. The Warburg Measurements were accepted by everybody.
MR. LARSON: Yes.
MR. ARNOLD: But so I said we would try and probably its four chlorophylls per CO2 reduced at maximum and it could be that one chlorophyll took up four quanta, and obviously we knew the answer. When we made the measurements, it turned out that there were 2,500 or so chlorophyll molecules per…
MR. LARSON: Amazing a result.
MR. ARNOLD: Just utterly unbelievable at first. Gaffron, Hans Gaffron was one of the photo researchers at that time. He wrote a paper and pointed out that it had to be that way. Nobody had taken the absorption coefficient of chlorophyll and found out how big the cross-section was for one chlorophyll molecule. Photosynthesis saturated that intensity far too low to have put light on all the chlorophyll. Anybody who had made the measurement should have found that years before. That discovery should never had…
MR. LARSON: That’s amazing.
MR. ARNOLD: …never been made with a slide rule, never been made. Nobody had compared the two. 
MR. LARSON: That’s an amazing discovery there.
MR. ARNOLD: You combine this discovery with the high efficiency. You see, Warburg found four quanta. It takes three to furnish the CO2, so its 75 percent efficient. How does it possibly work? Well, at the present time, the idea is if this was a sheet of chlorophyll or an object, light can hit anywhere, run quickly over to a place called reaction center and do the photosynthesis. The customs to call this antenna chlorophyll. In the sense of a radio antenna, picks up the wave and brings it down to a point. It’s hard to believe that the reduction doesn’t occur at all at 25,000, you see. It almost has to be at one point. These points are called reaction centers for mostly they are hypothetical, but in the case of purple bacteria, they had been isolated, and one of them can be made to do something back and forth to work. This experiment has led to a big study of this mechanism of photosynthesis. One of the main researchers was Pearlstein who was here in Oak Ridge, and is now at Indianapolis University there. He’s head of the Physics Department. There is a man whose name I forgot at San Diego who’s got into this field, and they are finding out where each chlorophyll is and how they are arranged. The general feeling is that in five or ten years from now we’ll know the mechanism, the microelectronics, if you will of the chloroplasts. 
MR. LARSON: Well that’s amazing. Of course there isn’t anything more important so far as life is concerned then to know about this most important reaction in the development of all living things. 
MR. ARNOLD: Is it all right to ask a question? 
MR. LARSON: Sure.
MR. ARNOLD: You can take it out. Do you want me to go on with that, or…?
MR. LARSON: Let’s go on chronologically now. You were doing this work at…
MR. ARNOLD: Cal Tech.
MR. LARSON: …Cal Tech, which was about 1932 now.
MR. ARNOLD: Yes, well let me say during that year I wrote and tried to get into a place in astronomy.
MR. LARSON: Oh yes. 
MR. ARNOLD: The best offer I had was $500 and a house my wife could live in, but no money for food or tuition or books. All this time Emerson argued, go do your degree in biology. For me then biology was a stepping stone, passing it up there. But Emerson said could he write to [William] Crozier. Now Emerson, after getting his degree with Warburg, spent a year or so at Harvard teaching. Crozier had a Department of Physiology. Crozier had an idea that physiology should be for plants, animals, and bacteria, all together. It didn’t pan out, but that’s what… He wrote him and back comes an offer with a salary to be a graduate student in biology. So my wife and I went to Harvard and I’m a graduate student. I’ve had one course while I was the assistant; I took a course in Gen. Ed. Took genetics and had some papers out that were interesting. Crozier said well if you’re going to be a biologist, you start at the beginning. So I started with freshman biology, cutting up earthworms, all those things.
MR. LARSON: The standard experiments. Frogs and embryology and all those things.
MR. ARNOLD: All right. I took the undergraduate biology, worked on my thesis, worked for the department, and I put the thesis together and got my degree in ’35. 
MR. LARSON: Oh yes. 
MR. ARNOLD: Is it all right?
MR. LARSON: Yes. 
MR. ARNOLD: You can take out things you don’t want…
MR. LARSON: It’s fine. But as I say, this is just informal and casual and all of these important scientific facts emerge in a chronological order which is… so you got your degree then in biology…
MR. ARNOLD: In what was called general physiology, but since Crozier had them all mixed in together, you would say it was in plant physiology.
MR. LARSON: Oh yes. 
MR. ARNOLD: And am I going too long?
MR. LARSON: Oh no. This is fine. 
MR. ARNOLD: Well, during these three years that I was a graduate student, from different parts of the experiments people came out who couldn’t repeat Warburg’s Four Light Quanta.  You see, they, and Emerson was worried about it and wrote to me that they all found more. So part of my thesis was a new measurement of a quantum that I invented because a fellow named [H.L.] Callendar had invented a thing called a radio balance. I don’t know if you have ever heard of that. 
MR. LARSON: No, I’ve never heard of that.
MR. ARNOLD: But there had been an argument about beta rays; did they give off, how much energy they gave off? They did this to measure the heat from beta rays. So my idea was to put plants in there, turn a light on and if they were doing photosynthesis, the energy that got tied up in photosynthesis wouldn’t show on the calorimeter. And then kill the plants without changing anything else. Now all the energy would go to heat and the ratio would give me the efficiency of photosynthesis. 
MR. LARSON: Oh yes.
MR. ARNOLD: Well the quantum yield turned out to be 12. 
MR. LARSON: Oh.
MR. ARNOLD: Ten, 11, 12, in that range.
MR. LARSON: Oh, I see.
MR. ARNOLD: Not four. Well, I didn’t believe it because well, Warburg was the boss.
MR. LARSON: Oh, yes, of course. He was a grand old man in this whole area.
MR. ARNOLD: Well now Harvard had a fellowship called a Sheldon Fellowship. It originally set up that when you got your degree you took a trip to Europe or something to round off your education. But it had been changed that you could, people used it for scientific work. There were about 12 of these; anyhow, there was one more than the number of departments. The custom, it sort of was that each department nominated somebody for the Sheldon Fellowship and a spare, an alternate. All the firsts got one, and then the entire faculty would deliver one more. The man that wanted me stopped me in the hall one day and says, “Arnold, if you were given a Sheldon Fellowship, what would you do?” Oh I said, “I would go to Berkeley and take Oppenheimer’s course in quantum mechanics.”
MR. LARSON: Oh yes.
MR. ARNOLD: He said, “Are you serious?” I said, “Yes. Everybody in the Physics Department here thinks it’s one of the best.” So he turned that in. well, I don’t know what happened, but you can imagine they started looking at the seconds and here was somebody that was in two departments. (Laughter)
MR. LARSON: Oh yes.
MR. ARNOLD: So I got two votes.
MR. LARSON: I’ll be darned.
MR. ARNOLD: Anyhow, I got the Sheldon Fellowship…
MR. LARSON: Oh wonderful.
MR. ARNOLD: …and I went to Berkeley and continued on this experiment on the quantum deal. Again I got the same answer. In the meantime, I wanted to work with [C.B.] Van Niel. Van Niel, you know was the great name in microbiology. 
MR. LARSON: At Stanford?
MR. ARNOLD: At Hopkins branch station. So I applied with a fellowship with Van Niel and it was granted. 
MR. LARSON: This was about 1937 or something about that then. 
MR. ARNOLD: Yeah, I went down there and stayed there four years with Van Niel.
MR. LARSON: Oh yes. 
MR. ARNOLD: And the first part I worked on this calorimeter and then it was published by Farrington Daniels.
MR. LARSON: Oh yes.
MR. ARNOLD: He did it over. He got the same answer and I just didn’t have the nerve, you see. Then the Carnegie put up the money for Emerson to do a real job on the quantum yield. 
MR. LARSON: Oh yes.
MR. ARNOLD: And while I was with Van Niel, I got a Rockefeller Fellowship to go work with [George] Hevesy to learn the technique of tracers. Hevesy was making the most success with them.  
MR. LARSON: As a matter of fact, had Hevesy been awarded the Nobel Prize by then?
MR. ARNOLD: Not yet.
MR. LARSON: Not yet. 
MR. ARNOLD: And that was there that I met [Otto Robert] Frisch and the story about the… I came back to Stanford and was made assistant professor in biology for a three year appointment.
MR. LARSON: Now when you, this was a Rockefeller Fellowship to spend that time at Bohr’s Laboratory. Hevesy of course is a grand old man of radioactive tracers…
MR. ARNOLD: Oh he was marvelous.
MR. LARSON: …and applications and such a tremendous… I met him shortly after the war. He was a…
MR. ARNOLD: I explained to Hevesy that I was mostly learning the techniques, the instruments so I worked most of the time with Hevesy’s assistant Hilda Levi who then later went to Sweden. She’s just written a book on his life. So Hevesy I talked with him lots of times, but the actual experimenting was done with Hilda Levi.
MR. LARSON: I know in my study of radioactivity, I’ve accumulated books. I still have a copy by Hevesy and [Fritz] Paneth. Classic book in the field.
MR. ARNOLD: I’ve had that.
MR. LARSON: So, well, then as a result of you being there at the Laboratory, you were presumably learning all of the techniques of Hevesy’s and using radioactive tracers and so on, I suppose?
MR. ARNOLD: Yes, but particularly the counters and the method of counting solvents and so on.
MR. LARSON: And the application of the Geiger counters and…
MR. ARNOLD: When I came back, I knew Stan Carson and Sam Reuben were using radioactive carbon to study chemical reactions. 
MR. LARSON: Oh yes. Sure. But I want to back up just a bit on this incident where you were there studying with Hevesy when Lise Meitner and Frisch came…
MR. ARNOLD: That’s right.
MR. LARSON: …through with this momentous discovery.
MR. ARNOLD: Well Frisch was working there.
MR. LARSON: Frisch was actually there?
MR. ARNOLD: Yes.
MR. LARSON: So you knew him in connection to your work right there in the laboratory.
MR. ARNOLD: Yes. It isn’t very big. 
MR. LARSON: No, I’ve visited there. I know. So I was wondering if you could just recount what your experience with Frisch was on this particular momentous discovery there.
MR. ARNOLD: Well, I don’t remember the dates, but [Otto] Hahn and [Fritz] Strassmann made the announcement that they got light elements out of uranium.
MR. LARSON: Yes. 
MR. ARNOLD: Everybody was simply astounded at that you see. And Frisch had gone over to visit his aunt who was in Sweden.
MR. LARSON: Yes. That’s Lise Meitner.
MR. ARNOLD: Now Hilda Levi, Meitner and Frisch had all been chased out by Hitler as you know.
MR. LARSON: Yes.
MR. ARNOLD: And they got talking and they worked out this idea that if a nucleus of an atom could pull off, there would be enough energy to push it apart, you see.
MR. LARSON: Oh yes. So into two approximately equal…
MR. ARNOLD: Yes, and Frisch, well, I wasn’t in these conversations with Bohr and so forth, and when he got the idea, he thought of trying this famous experiment with a counter, essentially a proportional counter with some uranium in it. 
MR. LARSON: Oh yes. And in your work, you were already using proportional counters.
MR. ARNOLD: Yes, they were. Well, I came to work and Hilda Levi said, “Frisch has got a marvelous experiment in the basement.” She says, “Go down and see it.” So I went down and they had these little cylinders about that long and so big around that had iridium and beryllium, or whatever gives off on the end of a little rod.
MR. LARSON: Yes, iridium, beryllium source of neutrons.
MR. ARNOLD: Yes, you can look at the oscilloscope and see these little spikes, push this under the counter and see these big spikes until you took it away. 
MR. LARSON: Oh yes. So you have the small energies from the alpha and then all of a sudden, great big spikes from the fission fragments.
MR. ARNOLD: And they would depend on how far you were away from it with the neutrons, how often you got them.
MR. LARSON: Oh yes, so convincing. That’s very convincing and such a simple demonstration too at that.
MR. ARNOLD: Oh, I had gone back up to the lab when Frisch poked his head in about the name. He said, “You work in a biology lab,” he said, “What do you call it when a bacterium divides?” I told him binary fission. He said, “I don’t want a two word name. Can you use fission alone?” I said, “Yes, you can use it alone.” 
MR. LARSON: Well, fine.
MR. ARNOLD: It’s a good thing he didn’t chose the whole thing because some of them split into three. 
MR. LARSON: Oh yes. As a matter of fact in connection with the name, I did an interview with Luis Alvarez at Berkeley and we happened to be talking about fission and somehow or other I used the words binary fission and he said, “Well, you know, I discovered ternary fission.” He was the one who identified the three small chunks there. So he said, “I’m given credit for the ternary fission.” So, but that’s a very interesting point in history and one of the amazing things there is some of these very world shaking events like seeing the uranium atom split in half. All of the other people in the world like Fermi and Joliot-Curie and everybody else had missed in working, working all these years and yet here you saw this very simple apparatus in the basement, such obvious, indisputable proof.
MR. ARNOLD: It had been interpreted as adding and going up the chain and that wasn’t happening at all. 
MR. LARSON: Oh yes. 
MR. ARNOLD: That’s what messed the chemistry up. 
MR. LARSON: Of course if you had seen those spikes and had a little background, it would have I think been very obvious. It was missed by a lot of prominent people. Fine. Well, very good then. So, then how long did you spend in Denmark?
MR. ARNOLD: A whole year.
MR. LARSON: A whole year.
MR. ARNOLD: Essentially a year.
MR. LARSON: And then what…
MR. ARNOLD: Well I had a wife and daughter with me. We went over on a freighter because I wanted to see the Panama Canal. So we took…
MR. LARSON: That must have been a fine experience.
MR. ARNOLD: Well, it was kind of worrisome because there were rumors of war, you see…
MR. LARSON: Oh yes.
MR. ARNOLD: …on the way over. When we came back, we got into New York just before ships were zig-zagging and running without lights and all that. 
MR. LARSON: So then when you came back to the United States, where did you go?
MR. ARNOLD: Back to Stanford.
MR. LARSON: Back to Stanford?
MR. ARNOLD: See that was in the four years, I had been a… After I had been an assistant professor, which sounds nice, for about three months, I got a letter that the National Defense Research Committee...
MR. LARSON: Yes.
MR. ARNOLD: They found out that I was trained as a biologist, I mean physicist. They needed physicists. They wanted me to volunteer for, to work on anti-aircraft fire, which I didn’t want to do, you see. So I went to the President of Stanford and he said, now look, he says, if they ask us to release you, we’re going to. He said, you better volunteer. 
MR. LARSON: Oh yes.
MR. ARNOLD: So just before Pearl Harbor, I was put on this job and we went back to Fort Monroe, Virginia, just after Pearl Harbor, had Christmas on a train with our two kids. Trains were crowded, they were going by. It was a mess you know. I spent, well I forget, part of a year at Fort Monroe on this problem. We were looking to find a house there because there was ship building going on. Then it was decided to put this research part of the Kodak Company and so the, well I’m messing this up. Early in the war, the Army was sort of reorganized and anti-aircraft fire was put onto the Air Corps. Previously, it had been under Coast Defense and Fort Monroe was a Coast Defense place so they were going to move the whole thing to North Carolina, Camp David, which was an Air Force Base, but they didn’t. They decided to split the experimental part to Rochester. So, we moved to Rochester, my wife and two kids and I worked in Rochester, but spent the time on trains going to North Carolina for experiments and back to Rochester. 
MR. LARSON: Oh yes.
MR. ARNOLD: I heard an awful lot of cannons go off on these tests. That’s why my hearing is so bad now. And after, let’s see, this would be about ’44. The proximity fuse and automatic pointing had made the aircraft [inaudible] actually shooting the whole thing down.
MR. LARSON: Oh yes.
MR. ARNOLD: Tennessee Eastman wanted physicists so I was transferred down here, but on loan because there was still one optical experiment in Rochester that they wouldn’t let me go, I still had some responsibility for. So I was on loan here from Tennessee Eastman until the end of the war. I worked in the same building as Jane.
MR. LARSON: Oh yes. Then you...
MR. ARNOLD: Then when the war was over it was a lot of confusion, but it was announced that the Biology Division at X-10 which during the war had only been trying to determine the safe limits for… would be made into a regular Biology Division. Biology would become a research. Oh I was going to ask them for a job. 
MR. LARSON: Oh yes. 
MR. ARNOLD: Because in the meantime, my three years were up on my appointment, you see, and we, my wife and I liked Tennessee, but we didn’t like Rochester. It was so cold and all the snow.
MR. LARSON: Dark also.
MR. ARNOLD: So I joined the Biology Division to work on photosynthesis. 
MR. LARSON: Oh wonderful.
MR. ARNOLD: That was in ’46, right after the end of the war. 
MR. LARSON: So that turned out very well then.
MR. ARNOLD: Well do you want me to go onto this delayed light business?
MR. LARSON: Yes. That’s what I would like to, fine, make sure we cover that. 
MR. ARNOLD: All right. Most photosynthesis measurements were made on microscopic algae because you can handle it like a solution and they’ll do photosynthesis and you can pipette them. People were starting to work on chloroplasts themselves. I got interested in that because you can make more intimate contact with the chloroplasts than a cell and I was, I’m now talking about 1950. I was working with chloroplasts trying to find a [inaudible] experiment and Bernard Strehler, who’s now a professor at USC in Los Angeles came here as a post-doc from [William] McElroy at Johns Hopkins, who use to work with Waldo Cohn. He’s a very bright fellow and he had just invented a device for measuring ATP [Adenosine Triphoshate]. 
MR. LARSON: Oh yes. 
MR. ARNOLD: A mixture of fireflies that would measure ATP. You could mix them in and you cut off a light in front of a photo multiplier, you had ATP.
MR. LARSON: Oh yes.
MR. ARNOLD: And he was always enthusiastic about ATP, which you know to become more and more likely how cells handle energy. 
MR. LARSON: Yes. 
MR. ARNOLD: Like we use dollars to buy things, they use ATP to move energy around.  He came and said would I like to be in on one of the great discoveries in photosynthesis. Well who would object to that? He said that he had been thinking about it and ATP must be made in photosynthesis. It would be needed to carry out the chemistry. He had in preparation a firefly tail thing that could detect ATP and we could use my chloroplasts, mix them together and if they gave off light there was ATP, we would know light was making ATP. So we did the experiment and essentially at once, because we were both working on it. Sure enough we got light. We thought we’ve made this discovery ATP is coming out, but then you have to do the controls. So we put the fireflies by themselves in the light and the chloroplasts by themselves in the light. The chloroplasts were giving out the light. (Laughter) 
MR. LARSON: Oh. 
MR. ARNOLD: This was a very exciting discovery.
MR. LARSON: Well, yes it must have been.
MR. ARNOLD: Later I called it delayed light, you see. But it was exciting because everybody knew or thought they knew that excited chlorophyll lasted about 10 to the minus eight seconds. During that time, some process used part of the energy for photosynthesis. Now you wouldn’t expect anything with 10 to the minus eight seconds to be able to be seen in our experiments by hand closed shutters, you see. And besides, Gaffron had thought some years before that there was possibly some kind of delayed light. He’d taken a phonograph disk; he glued leaves on the top of the disk, fixed it so he could spin it very fast, shot a beam of blue light down on it and looked at it with a red filter so you wouldn’t see the blue. You could see the chlorophyll fluorescent was not drawn out into a line. There wasn’t any long, so everybody knew there was not long component, only the photo cell said there was. That’s what started the, our investigation of delayed light because you had to measure the lifetime, the decay curve, and the spectrum. The spectrum turns out to be the same as the fluorescents of chlorophyll. There is no doubt that it is chlorophyll fluorescents you’re seeing. As soon as we were sure of this, we went up to Champaign, Illinois, where Emerson was and where Herb [inaudible] was. These were the two people that you would see about… We stayed there a couple of days and explained the experiment, and sort of got their blessing.
MR. LARSON: Oh yes. With reassurance and all that.
MR. ARNOLD: We came back and got to work on it. About, I think it was about two years later, [Daniel] Arnon and the people at Berkeley found ATP coming from chloroplasts. Later Strehler set up our original experiment and put the filters in so that the photo multipliers would see only the light from the firefly tails and not from chlorophyll and the experiment was working. We threw it out because we did something else. 
MR. LARSON: That’s interesting how these are the unexpected things in science. 
MR. ARNOLD: Strehler went off on another subject, and I continued the delayed light and with the help of Jack Davidson, who you probably know over at X-10 now, we worked out the apparatus to make measurements and do the study, and Jim Asse was working with me when we got the apparatus ready. He made the real good spectrum of the omission of delayed light and…
MR. LARSON: Oh yes. 
MR. ARNOLD: Now this, I think I have covered all of that. This led to…
MR. LARSON: Yes. That is a fascinating story.
MR. ARNOLD: This led to two little more discoveries. 
MR. LARSON: Yes. Fine. 
MR. ARNOLD: The first one is about CO curves, now it had been known for many years that you could take out into the sunlight, expose them to sunlight, bring them in and put them in a pan and warm them on a stove and they would give off light. That was called CO curves. The phenomenon is energy stored, a thermal fluctuation can untrap it, and you get it back.  Also at X-10, they were using little glass rods in the badges for radiation detectors. The radiation would store in there. You would heat the rods and give off a flash of light. So you see it was essentially obvious to try if this light could make a CO curves.
MR. LARSON: Oh yes. 
MR. ARNOLD: Well we tried it and it works like a charm. You take, freeze a plant down to liquid nitrogen dry ice, put light on it, and heat it up and as you come up, the light omission gets faster and faster as the temperature goes up and you run out of traps and it comes down and you get a nice thing called a CO curve. The location of the heating rate lets you calculate the energy of activation. So once you can find out the steps in here, the energy. Now this has been carried on by a lot of people, particularly the Indian named Tactat who’s published on it and there are about six or so of these CO curves in plant material.  There is one very nice discovery about it. It was made by [Edward] Tolman and [Melvin] Calvin at Berkeley. They knew we were making CO curves. And they tried it. They found that if you, that if you freeze a plant in the dark, say to liquid nitrogen temperature, and give it a flash of light, then there is delayed light comes off for about a millisecond, a short term light goes off. You do it a few times and it won’t work anymore. 
MR. LARSON: Well that’s interesting.
MR. ARNOLD: But now if you warm it back up to room temperature and cool it back down in the dark, it will work again.
MR. LARSON: I’ll be darned. What an interesting phenomena? 
MR. ARNOLD: Well I think it has a simple explanation. Imagine that over this photosynthetic unit, this chlorophyll, the light is running around from one chlorophyll to the other and it drops into a trap. Then that leaves a hole, and at the same time a hole can go into a trap you see, by an electron going in that leaves you a pair. Then you could have a recombination of the electrons and whole pair and get out chlorophyll fluorescents. As soon as you filled all the traps, it would stop.
MR. LARSON: Oh yes.
MR. ARNOLD: So you’ve got to get up to temperature and get empty. I think that’s probably the explanation. Now we’ll know in five or ten years.
MR. LARSON: Oh yes. 
MR. ARNOLD: When these people finish out how it worked. Well that’s one more discovery, and then I’ll be all talked out.
MR. LARSON: Well that’s fascinating.  
MR. ARNOLD: It occurred to me that maybe in chloroplasts you could affect the delayed light by putting electrodes, like in electrolysis; maybe I could pull those electrons away and turn it off. That would be a nice way to… so we tried the experiment and it goes the other way. 
MR. LARSON: Oh. (Laughter)
MR. ARNOLD: Well…
MR. LARSON: Nature can be most perverse sometimes.
MR. ARNOLD: It’s the most astonishing reaction if you have chloroplast, put a voltage across them, the light goes up and you can go up and make it ten times bigger, make it 50 times bigger, make it two times bigger, just depending on the voltage, and I think the explanation is that if you have a trap, now suppose here’s a trap and I’ve got an electron. The thermal fluctuation is going to put it up in the trap, you see. Now you can get the light out. If you’ve got an electric field, it’s like tipping it. If you’re trying to jump from the floor onto a chair, it’s easier on the side of a hill with the chair below you and then the field simply forms a hill there. 
MR. LARSON: Oh yes.
MR. ARNOLD: Well it’s very fast also. If you put 60 cycles on, you see 120 waves increasing the delayed light to zero in between. Now this hasn’t been studied very much, but there is an actual thesis from Holland on this. He investigated the whole thing and actually made a kind of CO curve by running the voltage up from zero to a very high voltage and again, it goes up and comes down. Well I guess that’s enough about that.
MR. LARSON: Well what a wonderful explanation of that. It’s a really…
MR. ARNOLD: Is that what you wanted?
MR. LARSON: Yes, this has given us a wonderful exposition of the…
[End of Interview]