Pump--probe measurements of state-to-state rotational energy transfer rates in N sub 2 ( v =1)

Journal Article · Sat Dec 01 04:00:00 EST 1990 · Journal of Chemical Physics; (USA)

DOI:https://doi.org/10.1063/1.459370· OSTI ID:6045344

Sitz, G O; Farrow, R L ^[1]

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1. Combustion Research Facility, Sandia National Laboratories, Livermore, CA (USA)

We report direct measurements of the state-to-state rotational energy transfer rates for N{sub 2} ({upsilon}=1) at 298 K. Stimulated Raman pumping of {ital Q}-branch ({upsilon}=1{l arrow}0) transitions is used to prepare a selected rotational state of N{sub 2} in the {upsilon}=1 state. After allowing an appropriate time interval for collisions to occur, 2+2 resonance-enhanced multiphoton ionization is used (through the {ital a} {sup 1}{Pi}{sub {ital g}}{l arrow}{ital X} {sup 1}{Sigma}{sup +}{sub {ital g}} transition) to detect the relative population of the pumped level and other levels to which rotational energy transfer has occurred. We have performed a series of measurements in which a single even rotational level ({ital J}{sub {ital i}}=0--14) is excited and the time-dependent level populations are recorded at three or more delay times. This data set is then globally fit to determine the best set of state-to-state rate constants. The fitting procedure does not place any constraints (such as an exponential gap law) on the {ital J} or energy dependence of the rates. We compare our measurements and best-fit rates with results predicted from phenomenological rate models and from a semiclassical scattering calculation of Koszykowski {ital et} {ital al}. (J. Phys. Chem. {bold 91}, 41 (1987)). Excellent agreement is obtained with two of the models and with the scattering calculation. We also test the validity of the energy-corrected sudden (ECS) scaling theory for N{sub 2} by using our experimental transfer rates as basis rates ({ital J}={ital L}{r arrow}0), finding that the ECS scaling expressions accurately predict the remaining rates.

• OSTI ID: 6045344
• Journal Information: Journal of Chemical Physics; (USA), Journal Name: Journal of Chemical Physics; (USA) Vol. 93:11; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400800 -- Combustion
Pyrolysis
& High-Temperature Chemistry
640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
CHEMICAL REACTIONS
COLLISIONS
COMBUSTION
DIAGNOSTIC TECHNIQUES
ELEMENTS
ENERGY LEVELS
ENERGY TRANSFER
ENERGY-LEVEL DENSITY
EXCITED STATES
IONIZATION
KINETICS
LASER SPECTROSCOPY
MOLECULE COLLISIONS
MOLECULE-MOLECULE COLLISIONS
MULTI-PHOTON PROCESSES
NITROGEN
NONMETALS
OPTICAL PUMPING
OXIDATION
PHOTOIONIZATION
PUMPING
RAMAN SPECTROSCOPY
RESONANCE
ROTATIONAL STATES
SPECTROSCOPY
TEMPERATURE DEPENDENCE
TEMPERATURE MEASUREMENT
THERMOCHEMICAL PROCESSES