optical pumping alex

8/7/2019 Optical Pumping Alex

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I. EXPERIMENTAL PROCEDURE

a temperature of 50C was used for all data acquisition, except for the innovative part of the

experiment when temperature was varied.

INSERT THIS PICTURE, and THIS PICTURE, TOO The Teach-Spin apparatus was set-up

with the following linear set-up configuration: RF discharge lamp, converging lens, interference

filter, linear polarizer set to 45, 14 -wave plate, rubidium absorption shell, diverging lens, and opti-

cal detector. The focal length of the lenses was found by shining a flashlight through the converg-

ing end, and aiming the lens at the table; using this as a first guess of where to place the lenses

respective to their emitter/detector, and then moving them until a maximum signal was viewed

on the galvanometer. All instrument positions were then recorded.

!!! THEORY To obtain circularly polarized light, linearly polarized light must be altered to

have equal magnetic and electric amplitudes, and the fields must be 90 (2 ) out of phase with

each other. The linearly polarized light is shone on a 14 -waveplate which will put the electric and

magnetic field 90 out of phase with each other, and will also equate the two amplitudes if the

light is shone 45 to the 14 -wave plate (6), and both conditions are satisfied.

To test if the light was circularly polarized, a second linear polarizer was placed before the last

lens, and rotated. It was observed that the signal was insignificantly affected when the polarizer

was rotated, indicating circularly polarized light was achieved.

All magnetic and conductive materials were then removed from the area of the apparatus,

except for the handle connected to the black covering box. The handle was found to be somewhat

ferromagnetic, but nothing could be done to replace it.

-!With the main field unplugged, the external magnetic field was then cancelled out by apply-

ing an opposing magnetic field using the sweep coil. The entire apparatus was also aligned to

maximize the galvanometer reading, and the vertical magnetic field was adjusted to minimize the

zero-field transition bandwidth. With the external field cancelled, a digital volt meter (DMV) was

used to measure the voltage used in the sweep and vertical field coils through a 1- resistor, and

thus was also equivalent the current used. These current values were recorded every time the ex-

ternal field was cancelled. With the current known, as well as the coil constants given on page 3-14

of the manual, the magnitude and direction of Earths magnetic field can be roughly calculated.!-

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1. Finding the g-Factor and Coil Constants

Using the coil constants given in the TeachSpin manual, the lambda-g factor can be calculated

for Rb87 and Rb85. Using equation 2F-2 from the TeachSpin manual;

= gFB

hB, (1)

where is the transition frequency in Hz, and the magnetic field B is in units ofGauss, andB

h =

1.3669 MHzGauss , the gF was experimentally found by varying the RF frequency and measuring the

current at the resonant peaks of Rb87 and Rb85. The difference of the resonance currents and the

zero-field peak current was taken, and converted to magnetic field using the given coil constants.

Then, was plotted againstB

h B; the resultant plot gave two straight lines, one for each isotope,

with slopes equal to their respective gF values.

Similarly, the coil constants can be found by taking the known values ofgF for each isotope (13

and 12 ), and obtaining a B, where Ican be solved for by dividing B by the number of turns for each

coil.

A. Quadratic Zeeman Effect

The Quadratic Zeeman effect was observed by turning on the RF at MHz frequencies. Mathcad

was used to calculate the magnetic field for each resonance at certain frequencies, the theoretical

number of peaks visible was also calculated. To avoid the double photon effect, the intensity

was adjusted so that the double photon effect was minimized while still being able to view the

quadratic effect peaks.

B. Rabi oscillations and Transient Effects

Rabi oscillations and transient effects were viewed by setting the RF to a low resonant fre-

quency (hundreds of kHz) and by using a function generator to produce a square wave with a

peak-to-peak value of 5 Volts, and a frequency of 5 Hz. The square wave made simulates turning

on and off the RF abrubtly. This allowed us to view the excitation time and relaxation time of the

Rubidium atoms over different temperatures.

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RESULTS AND DISCUSSION plotting was done in kalaeidagraph and excell

the value found of Earths field was 406.4 mG compared to NOAAs 547 mG. Though no error is

attributed, a reason the value may be in compatible may be due to the environment in the room,

were surrounded by AC current, and conducting metal in the walls which could alter and screen

any outside external field.

INSERT GRAPH FROM pg 16 the g factors obtained were .506 and .339 compared to the

accept values of 13 and12

INSERT GRAPHS FROM pg 24 and 25 for the Quadratic Zeeman effect, only four of the five

calculated peaks were observed for Rb87 , here is a list of the recorded peaks and the calculated

peak positions measured calc 5.711898416 5.697

5.718272244 5.706

5.725155979 5.715.73178476 5.72

5.729

5.739

For Rb85, only six of the ten calculated peaks were observed.

measured calc 9.71853584 8.528

9.72158609 8.534

9.74293784 8.549

9.78564134 8.555

9.80800984 8.57

9.83037834 8.576

8.591

8.597

8.612

8.634

measuring the time constant t over different temperatures, and plotting the data, it appears that

there is a jump in the time constant around 63.5C. After an apparently linear trend from 30-60C,

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a sharp jump in the time constant ruins the linearity and calls for an explanation for itself.

we know this and that, but due to the difficulty of this experiment being set on hard-mode, it

has been very challenging to analyze the data and interpret the results.

FIG. 1: Simulation of structure evolution using kinetic Monte Carlo

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