HR: 1330h
AN: SA12A-1074 [PDF]
TI: Laboratory Study of O$_2({b}^1\Sigma_{{g}}^{+}, \upsilon = 1)$ Collisional Removal at Thermospheric
Temperatures
AU: Wouters, E R
EM: eloy.wouters@sri.com
AF: Aeronomy Group, Molecular Physics Laboratory, SRI International, 333 Ravenswood Avenue, Menlo Park, CA
94025 United States
AU: Wouters, E R
EM: eloy.wouters@sri.com
AF: University of Maryland, Institute for Physical Science and Technology, College Park, MD 20742 United States
AU: Pejakovi\'{c}, D A
EM: dusan.pejakovic@sri.com
AF: Aeronomy Group, Molecular Physics Laboratory, SRI International, 333 Ravenswood Avenue, Menlo Park, CA
94025 United States
AU: Phillips, K E
EM: kristin.phillips@sri.com
AF: Aeronomy Group, Molecular Physics Laboratory, SRI International, 333 Ravenswood Avenue, Menlo Park, CA
94025 United States
AU: Phillips, K E
EM: kristin.phillips@sri.com
AF: Department of Physics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093 United States
AU: * Kalogerakis, K S
EM: ksk@sri.com
AF: Aeronomy Group, Molecular Physics Laboratory, SRI International, 333 Ravenswood Avenue, Menlo Park, CA
94025 United States
AB:
In the Earth's thermosphere, energy transfer from O($^1D$) to O$_2$ generates oxygen molecules in the $\upsilon$ = 0 and 1
levels of the O$_2(b^1\Sigma_{g}^{+})$ state. The emissions in the O$_2(b^1\Sigma_{g}^{+} - X^3\Sigma_{g}^{-})$ system
(Atmospheric Band) present a major component of the Earth's airglow. Interpretation of the measured intensities of O$_2$
Atmospheric Band emissions can yield altitude profiles of oxygen atom density and local temperature in the lower
thermosphere. To achieve this goal accurate laboratory measurements of the collisional removal rate coefficients of O$_2(b,
\upsilon = 1)$ and their temperature dependence are essential. Atmospheric observations suggest that the relevant colliders
for the removal of O$_2(b, \upsilon = 1)$ in the lower thermosphere are O$_2$ and O($^3P$). We report measurements of the
rate coefficients for the collisional removal of O$_2(b, \upsilon = 1)$ by O$_2$, N$_2$, and CO$_2$, at temperatures in the
range 300--1000 K. A state-specific two-laser technique is used, in which the visible output of the first laser directly
excites O$_2$ to O$_2(b, \upsilon = 1)$, and the ultraviolet output of the second laser probes the O$_2(b, \upsilon = 1)$
population by resonantly enhanced multiphoton ionization via the $\upsilon= 4$ level of the $d^1\Pi_g$ Rydberg state. The
temporal evolution of the O$_2({b}, \upsilon = 1)$ population is monitored by varying the time delay between the two laser
pulses. The rate coefficient of the collisional removal of O$_2(b, \upsilon = 1)$ by O$_2$ increases monotonically with
temperature from about 1.5 $\times$ 10$^{-11}$ cm$^3 $s$^{-1}$ to about $6\times10^{-11}$ cm$^3 $s$^{-1}$ in the range
300--1000 K. Experiments with colliders N$_2$ and CO$_2$ determine the upper limits for the removal rate coefficients of
O$_2({b}, \upsilon = 1)$ by N$_2$ and CO$_2$ to be 2 orders of magnitude smaller. This work extends previous studies of
O$_2({b}, \upsilon = 1)$ at room and low temperatures.$^{1,2}$ We are currently planning experiments to investigate the
collisional removal of O$_2({b}, \upsilon = 1)$ by O atoms.\\ This study was supported by the NSF's Grant ATM-0209229. The
participation of K. Phillips in this project was funded by NSF's Research Experiences for Undergraduates (REU) Program (Grant
\mbox{PHY-0097861). } We wish to thank Drs. Richard A. Copeland and Tom G. Slanger for many insightful comments and
discussions. \\ 1. H. I. Bloemink, R. A. Copeland, and T. G. Slanger, J. Chem. Phys. {\bf 109}, 4237 (1998).\\ 2. E. S.
Hwang, A. Bergman, R. A. Copeland, and T. G. Slanger, J. Chem. Phys. {\bf 110}, 18 (1999).
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0310 Airglow and aurora
DE: 0394 Instruments and techniques
DE: 0399 General or miscellaneous
SC: SPA - Aeronomy [SA]
MN: 2003 Fall Meeting