Before we could begin the experiment, we had to construct the apparatus as shown previously. After everything was in place, we used a detector for the Wavemeter Junior and blocked the pump beam. The reading on the Wavemeter Junior was the wavelength of the beam being emitted by the laser. To adjust this wavelength, we made slight adjustments to the current and temperature controls until the wavelength on the Wave Meter Junior read 794.98 nm. This wavelength is in the range of wavelengths of photons emitted in a transition from the 5p_1/2 to the 5s_1/2 level.

After the wavelength of the laser had been tuned, we connected the function generator to the current control device and the photo diode to the oscilloscope in order to view the absorption spectra. The function generator was putting out a ramp voltage of 0.046 volts from peak to peak. For every 1 volt change, the current changed 100 mA. This created a current that was fluctuating very slightly and producing a range of wavelengths from the diode laser. Some of these wavelengths stimulated excitation of the atoms in the rubidium cell. This absorption resulted in a beam of reduced intensity at certain frequencies exiting the rubidium cell. A photo diode was used to detect the laser beam after exiting the Rb cell.

Another photo diode was used to detect the emission from the Rb cell. We placed a photo diode at the side of the cell to detect the photons that were being emitted in all directions as electrons returned to lower energy levels. Both of the photo diodes were initially connected to an oscilloscope in order for us to view the spectra. In order to graph the spectra and the triangle wave from the function generator, we then connected the photo diodes and the function generator to a Pasco Signal Interface and used a program called Science Workshop to capture the data. We transported the data into Quattro Pro, a spreadsheet program, and graphed the data. The graphs initially appeared as transmittance vs. time, but we converted the x-axis to a frequency scale.

After generating the graphs of the emission and absorption spectra, we were able to measure the frequency difference between peaks. This measurement gave us the frequency difference between the transition levels in the energy level diagram.

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