Theoretical investigation of state-changing thermal collisions between Rydberg atoms and ground state noble gas atoms

Thesis/Dissertation · Sat Jan 01 04:00:00 EST 1983

OSTI ID:5092725

Davis, I L

Two methods for calculating state-changing collisional matrix elements, and hence angular-momentum-mixing cross sections, are presented for a ground state noble gas atom colliding with a Rydberg atom at thermal energies. The first is a fully quantal method using Monte Carlo integration to perform the necessary nonseparable fifteen-dimensional collision integrals. The equations are developed for general treatment in the first and higher Born approximations, the distorted wave approximations,and several close-coupling schemes. The Monte Carlo method is carefully developed and tested for use in the types of integrals involved, and variance reduction techniques are discussed and applied. The second method uses a Gegenbauer polynomial expansion of the -1/r/sup 4/ polarization potential to find the necessary matrix elements. It also employs the elliptic functions and elliptic integrals to calculate the classical trajectory of the ground state atom as it passes the ionic Rydberg core. This semiclassical method is easily transformed into a fully quantal method, retaining only the polarization potential feature, by integrating the translational wave function of the incoming ground state atom and the matrix elements calculated via the Gegenbauer polynomials. The equations of scattering for the first quantal method are then specifically developed for ground state helium colliding with Rydberg helium, and calculation of the l-mixing cross section for He(10/sup 1/P) is performed using over a half million random fifteen-dimensional points. The result, accurate to within a factor of two, gives a result of 1600 A/sup 2/ compared to the experimental value of 2580 +/- 590 A/sup 2/. This experimental value is within the variance of the Monte Carlo calculation.

• Research Organization: Utah State Univ., Logan (USA)
• OSTI ID: 5092725
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ATOM COLLISIONS
ATOM-ATOM COLLISIONS
BORN APPROXIMATION
COLLISIONS
CROSS SECTIONS
DATA
ELEMENTS
ENERGY LEVELS
EXCITED STATES
FLUIDS
FUNCTIONS
GASES
GROUND STATES
HELIUM
INFORMATION
MATRIX ELEMENTS
MONTE CARLO METHOD
NONMETALS
NUMERICAL DATA
POLYNOMIALS
RARE GASES
RYDBERG STATES
SCATTERING
THEORETICAL DATA
WAVE FUNCTIONS