Influence of Rotational Relaxation on Tropospheric OH Laser Induced Fluorescence Measurements

1982 ◽  
Vol 37 (6) ◽  
pp. 559-563
Author(s):  
K.-H. Gericke ◽  
F. J. Comes
Keyword(s):  
Ground State ◽  
Laser Induced Fluorescence ◽  
Rotational Relaxation ◽  
Water Molecules ◽  
Spectroscopic Methods ◽  
Additional Contribution ◽  
Rotational States ◽  
Fluorescence Measurements ◽  
Fast Relaxation ◽  
Electronic Ground

Abstract Rotational relaxation of OH molecules in the 2II electronic ground state has been observed to occur in collisions with water molecules with gas kinetic probability. It causes an additional contribution to the already well known sources of interference when LIF is used to monitor tropospheric OH. As the laser generated OH is originally produced mostly in high rotational states, the fast relaxation phenomenon leads to a further population of OH in low rotational states. These states are used to monitor tropospheric OH by spectroscopic methods. The observed effect therefore increases the interference. A mathematical analysis is presented, revealing the effect of all relevant parameters.

scholarly journals Infrared–ultraviolet double resonance measurements on the temperature dependence of rotational and vibrational self-relaxation of NO(X2Π, υ = 2,j)

1994 ◽  
Vol 72 (3) ◽  
pp. 606-611 ◽  
Author(s):  
Michael J. Frost ◽  
Meezanul Islam ◽  
Ian W.M. Smith
Keyword(s):  
Ground State ◽  
Energy Exchange ◽  
Double Resonance ◽  
Excited Level ◽  
Laser Induced Fluorescence ◽  
Spin Orbit ◽  
Time Resolved ◽  
Fluorescence Measurements ◽  
Direct Measurements ◽  
Electronic Ground

Infrared–ultraviolet double resonance experiments have been performed to measure the rates of rotational and vibrational self-relaxation in NO at three temperatures: 295 K, 200 K, and 77 K. Pulses of tunable infrared radiation from an optical parameteric oscillator have been used to excite molecules into selected rotational levels (j = 0.5, 6.5, or 15.5) in the [Formula: see text] vibronic component of the X2Π electronic ground state of NO. Loss of population from the initially excited level was observed by making time-resolved laser-induced fluorescence measurements on appropriate lines in the A2Σ+ − X2Π(2,2) band. The rate constants for removal of population from specific rovibronic levels are essentially independent of j and at 295 K agree well with previous direct measurements on a range of υ, j levels. The rotationally thermalized population in υ = 2 relaxes by vibration–vibration (V–V) energy exchange, NO(υ = 2) + NO(υ = 0) → 2 NO(υ = 1), at a rate which is almost independent of temperature and which seems to be uninfluenced by the presence of spin-orbit degeneracy in, and attractive forces between, the NO collision partners.

The ground state of Na2

1989 ◽  
Vol 67 (9) ◽  
pp. 912-918 ◽  
Author(s):  
O. Babaky ◽  
K. Hussein
Keyword(s):  
Fourier Transform ◽  
Gas Phase ◽  
Ground State ◽  
Laser Induced Fluorescence ◽  
Rotational Relaxation ◽  
Fixed Frequency ◽  
Molecular Constants ◽  
Vibrational Levels ◽  
Laser Frequencies ◽  
Ion Laser

The laser-induced fluorescence of the [Formula: see text] and [Formula: see text] transitions of Na2 are analysed, using high resolution Fourier transform spectroscopy. Fixed-frequency ion-laser lines (4880 and 4765 Å (1 Å = 10−10 m) from Ar+ and 6471 and 4762 Å from Kr+) together with laser frequencies from a ring dye laser, using rhodamine 6 G with λ = 5781.22 and 5796.80 Å, were used to excite Na dimer in the gas phase. Twenty-eight series of [Formula: see text] and [Formula: see text] systems have been assigned and analysed, and the strong transitions are accompanied by numerous rotational relaxation lines. Molecular constants of the [Formula: see text] state were calculated with high precision from simultaneous least-squares fits to 1410 lines assigned to the A–X and B–X systems. These constants have been used to determine the Rydberg–Klein–Rees potential curve of the X ground state for vibrational levels up to ν = 62.

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