We have observed the evolution of cold Rydberg gases and ultracold plasmas in an environment that allows for the control of interactions of the blackbody radiation temperature from 4K to 300K. The work in this thesis describes the influence of initial densities, populations, excitation state, evolution time and thermal background temperature on the evolution of cold Rydberg gases as well as directly excited ultracold plasmas. With some initial ionization, cold-Rydberg-atom gases easily develop a positive space charge that traps electrons for times on the order of tens of mus. This acts as a catalyst for electron-Rydberg atom collisions, increasing the collision probabilities by orders of magnitude and profoundly altering the final state of the Rydberg gas. Using state-selective field ionization, we have provided direct proof that these collisions cause changes in l-states, and we have seen the first experimental evidence that they also lead to inelastic n-changing collisions, as predicted by theory. We have also found evidence for Rydberg-Rydberg collisions, enabled by the attractive electric-dipole forces between atoms in high-l states and possibly by van-der-Waal's interactions at very high-n . Thermal interactions are seen to influence the formation of a plasma from a cold Rydberg gas. Plasmas form more easily in the presence of a 300K radiation field than at 4K, due to the contribution of thermal ionization to the plasma formation. The background temperature also appears to affect the electron temperature in both the directly excited plasma and the plasma spontaneously formed from a cold Rydberg gas. In Rydberg atom gases that have undergone partial ionization, electron temperatures were estimated using the dependence of n-changing collisions on the electron temperature.We have observed the evolution of cold Rydberg gases and ultracold plasmas in an environment that allows for the control of interactions of the blackbody radiation temperature from 4K to 300K. The work in this thesis describes the influence of initial densities, populations, excitation state, evolution time and thermal background temperature on the evolution of cold Rydberg gases as well as directly excited ultracold plasmas. With some initial ionization, cold-Rydberg-atom gases easily develop a positive space charge that traps electrons for times on the order of tens of mus. This acts as a catalyst for electron-Rydberg atom collisions, increasing the collision probabilities by orders of magnitude and profoundly altering the final state of the Rydberg gas. Using state-selective field ionization, we have provided direct proof that these collisions cause changes in l-states, and we have seen the first experimental evidence that they also lead to inelastic n-changing collisions, as predicted by theory. We have also found evidence for Rydberg-Rydberg collisions, enabled by the attractive electric-dipole forces between atoms in high-l states and possibly by van-der-Waal's interactions at very high-n . Thermal interactions are seen to influence the formation of a plasma from a cold Rydberg gas. Plasmas form more easily in the presence of a 300K radiation field than at 4K, due to the contribution of thermal ionization to the plasma formation. The background temperature also appears to affect the electron temperature in both the directly excited plasma and the plasma spontaneously formed from a cold Rydberg gas. In Rydberg atom gases that have undergone partial ionization, electron temperatures were estimated using the dependence of n-changing collisions on the electron temperature.

Jan 1, 20041 citation

Influence of electric fields on background photo- and collisional ionization processes in Rydberg-atom collision studies

S. B. Hill, R. Parthasarathy, L. Suess +1 more

Studies of Rydberg atom collision processes, especially those with small reaction rate constants, are frequently complicated by spurious background signals associated with photoionization by thermal blackbody radiation and with ionization resulting from collisions with background gas. Here we demonstrate that the magnitude and relative importance of the signals that result from these processes are strongly influenced by the presence of an applied electric field. Possible causes of this dependence are discussed.Studies of Rydberg atom collision processes, especially those with small reaction rate constants, are frequently complicated by spurious background signals associated with photoionization by thermal blackbody radiation and with ionization resulting from collisions with background gas. Here we demonstrate that the magnitude and relative importance of the signals that result from these processes are strongly influenced by the presence of an applied electric field. Possible causes of this dependence are discussed.

Physical Review AJun 13, 20002 citations

Two body and multibody interaction in a cold Rydberg gas

Jianing Han, Tom Gallagher

Bulletin of the American Physical SocietyMay 23, 20090 citations

Reply to “Comment on ‘Measurement of the lifetimes of S and D states below n=31 using cold Rydberg gas”’

L. L. Caliri, Luís Gustavo Marcassa

In response to the preceding Comment, we present important experimental information on our $S$ , $P$ , and $D$ Rydberg lifetime measurements for $^{85}\mathrm{Rb}$ using a sample of cold Rydberg atoms. We analyze and discuss the implications of blackbody radiation transfer on our results. We also discuss the limitation of the theory compared with our results.In response to the preceding Comment, we present important experimental information on our $S$, $P$, and $D$ Rydberg lifetime measurements for $^{85}\mathrm{Rb}$ using a sample of cold Rydberg atoms. We analyze and discuss the implications of blackbody radiation transfer on our results. We also discuss the limitation of the theory compared with our results.

Physical Review AJun 29, 200710 citations

In response to the preceding Comment, we present important experimental information on our

S

P

, and

D

Rydberg lifetime measurements for

^{85}\mathrm{Rb}

using a sample of cold Rydberg atoms. We analyze and discuss the implications of blackbody radiation transfer on our results. We also discuss the limitation of the theory compared with our results.