We have measured the effect of the transfer of excitation on the population of the $3^{3}D$ state of helium. Through careful diagnosis of a proton beam passing through a long target chamber containing helium gas, we have been able to separate the various contributions to the light intensity from the $3^{3}D$ state. Our measurements were performed at target-gas pressures roughly two orders of magnitude lower than those of previously reported measurements. We measure the summation of the excitation-transfer cross sections ${\ensuremath{\sigma}}_{c}(n)$ for the transfer from an $n^{1}P$ state to the corresponding $n^{3}F$ state times the branching ratio ${B}_{\mathrm{n}}$ for radiative cascade to the $3^{3}D$ state, and obtain $\ensuremath{\Sigma}{B}_{n}{\ensuremath{\sigma}}_{c}(n)=2.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$ ${\mathrm{cm}}^{2}$ . This measurement enables us to relate the excitation transferred to the $3^{3}D$ state ${Q}_{T} (3^{3}D)$ to the excitation cross section of the $4^{1}P$ state $\ensuremath{\sigma}(4^{1}P)$. We obtain ${Q}_{T} (3^{3}D)=(1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15} {\mathrm{cm}}^{3})N\ensuremath{\sigma}(4^{1}P)$, an expression, which for the low pressures used in this experiment, is linear in the number density $N$ .We have measured the effect of the transfer of excitation on the population of the $3^{3}D$ state of helium. Through careful diagnosis of a proton beam passing through a long target chamber containing helium gas, we have been able to separate the various contributions to the light intensity from the $3^{3}D$ state. Our measurements were performed at target-gas pressures roughly two orders of magnitude lower than those of previously reported measurements. We measure the summation of the excitation-transfer cross sections ${\ensuremath{\sigma}}_{c}(n)$ for the transfer from an $n^{1}P$ state to the corresponding $n^{3}F$ state times the branching ratio ${B}_{\mathrm{n}}$ for radiative cascade to the $3^{3}D$ state, and obtain $\ensuremath{\Sigma}{B}_{n}{\ensuremath{\sigma}}_{c}(n)=2.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$ ${\mathrm{cm}}^{2}$. This measurement enables us to relate the excitation transferred to the $3^{3}D$ state ${Q}_{T} (3^{3}D)$ to the excitation cross section of the $4^{1}P$ state $\ensuremath{\sigma}(4^{1}P)$. We obtain ${Q}_{T} (3^{3}D)=(1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15} {\mathrm{cm}}^{3})N\ensuremath{\sigma}(4^{1}P)$, an expression, which for the low pressures used in this experiment, is linear in the number density $N$.

Physical Review AJun 1, 19722 citations

Excitation-Transfer Collisions between Rubidium and Helium Atoms

T. J. Beahn, W. J. Condell, Hirsch I. Mandelberg

An experiment is described which measures the collision cross section for transfer of excitation in rubidium by helium. Rubidium atoms are pumped to either the $^{2}P_{\frac{1}{2}}$ or $^{2}P_{\frac{3}{2}}$ state by irradiation with one of the resonance lines. Some excited rubidium atoms are transferred to the other $P$ state by collisions with helium atoms. The rubidium atoms then radiate both resonance lines. Measurements of the intensities of both resonance lines as a function of helium pressure are used to calculate the collision cross section. The cross section for $^{2}P_{\frac{1}{2}}$ to $^{2}P_{\frac{3}{2}}$ is 1.0\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}17}$ ${\mathrm{cm}}^{2}$ \ifmmode\pm\else\textpm\fi{}10% and for $^{2}P_{\frac{3}{2}}$ to $^{2}P_{\frac{1}{2}}$ is 1.2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}17}$ ${\mathrm{cm}}^{2}$ \ifmmode\pm\else\textpm\fi{}10%.An experiment is described which measures the collision cross section for transfer of excitation in rubidium by helium. Rubidium atoms are pumped to either the $^{2}P_{\frac{1}{2}}$ or $^{2}P_{\frac{3}{2}}$ state by irradiation with one of the resonance lines. Some excited rubidium atoms are transferred to the other $P$ state by collisions with helium atoms. The rubidium atoms then radiate both resonance lines. Measurements of the intensities of both resonance lines as a function of helium pressure are used to calculate the collision cross section. The cross section for $^{2}P_{\frac{1}{2}}$ to $^{2}P_{\frac{3}{2}}$ is 1.0\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}17}$ ${\mathrm{cm}}^{2}$\ifmmode\pm\else\textpm\fi{}10% and for $^{2}P_{\frac{3}{2}}$ to $^{2}P_{\frac{1}{2}}$ is 1.2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}17}$ ${\mathrm{cm}}^{2}$\ifmmode\pm\else\textpm\fi{}10%.

Physical ReviewJan 7, 196628 citations

We have measured the effect of the transfer of excitation on the population of the

3^{3}D

state of helium. Through careful diagnosis of a proton beam passing through a long target chamber containing helium gas, we have been able to separate the various contributions to the light intensity from the

3^{3}D

state. Our measurements were performed at target-gas pressures roughly two orders of magnitude lower than those of previously reported measurements. We measure the summation of the excitation-transfer cross sections ${\ensuremath{\sigma}}_{c}(n)$ for the transfer from an

n^{1}P

state to the corresponding

n^{3}F

state times the branching ratio

{B}_{\mathrm{n}}

for radiative cascade to the

3^{3}D

state, and obtain $\ensuremath{\Sigma}{B}_{n}{\ensuremath{\sigma}}_{c}(n)=2.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$

{\mathrm{cm}}^{2}

. This measurement enables us to relate the excitation transferred to the

3^{3}D

state

{Q}_{T} (3^{3}D)

to the excitation cross section of the

4^{1}P

state $\ensuremath{\sigma}(4^{1}P)$. We obtain ${Q}_{T} (3^{3}D)=(1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15} {\mathrm{cm}}^{3})N\ensuremath{\sigma}(4^{1}P)$, an expression, which for the low pressures used in this experiment, is linear in the number density

N

An experiment is described which measures the collision cross section for transfer of excitation in rubidium by helium. Rubidium atoms are pumped to either the

^{2}P_{\frac{1}{2}}

^{2}P_{\frac{3}{2}}

state by irradiation with one of the resonance lines. Some excited rubidium atoms are transferred to the other

P

state by collisions with helium atoms. The rubidium atoms then radiate both resonance lines. Measurements of the intensities of both resonance lines as a function of helium pressure are used to calculate the collision cross section. The cross section for

^{2}P_{\frac{1}{2}}

^{2}P_{\frac{3}{2}}

is 1.0\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}17}$

{\mathrm{cm}}^{2}

\ifmmode\pm\else\textpm\fi{}10% and for

^{2}P_{\frac{3}{2}}

^{2}P_{\frac{1}{2}}

is 1.2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}17}$

{\mathrm{cm}}^{2}

\ifmmode\pm\else\textpm\fi{}10%.