ORIENTATION AND ALIGNMENT OF METASTABLE P-2(3/2) THALLIUM ATOMS FOLLOWING PHOTODISSOCIATION OF TLBR

A study has been made of the oriented and aligned metastable 6 P-2(3/2) Tl atoms produced in molecular photodissociation. A low-pressure vapor of TlBr has been photolyzed in the two types of experiments by a beam of circularly and linearly polarized pulsed laser radiation at 266 nm. The resulting metastable Tl atoms were probed by a resonance atomic line at 535 nm from a discharge Tl lamp. A free precession of the oriented and aligned Tl atoms in an external magnetic field has been detected by a dichroism of the atomic vapors. The obtained signals were found to contain contributions from two different hyperfine (hpf) sublevels of the Tl atoms. The initial electronic degrees of atomic orientation and alignment at the moment of the laser pulse were obtained taking into consideration collisional depolarization of the produced atoms, hyperfine interactions in the atoms, optical thickness of the atomic vapors and hyperfine structure of the probe radiation. The initial degree of the orientation and alignment parameters were found to be: P = 19%+/-2% and A = 17%+/-4%, respectively. The quenching of the Tl (6 P-2(3/2)) atoms to their ground 6 P-2(1/2) state caused by collisions with TlBr molecules has also been studied and the quenching rate constant at the temperature of 670 K was found to be GAMMA(qu) = (3.1+/-0.3) x 10(-11) cm3/s.