Photofragment Dynamics

Photodissociation of Methyl Iodide via Selected Vibrational Levels of the B̃ (2E3/2)6s Rydberg State

“…Such behavior places a high value on well-characterized prototypical systems for which the detailed dynamical processes are understood. The photodissociation of methyl iodide, CH 3 I, via the à band in the near-ultraviolet (∼300 to 220 nm) provides one such system. − In recent years, there has been a significant effort to extend that understanding to photodissociation in the first Rydberg bands of CH 3 I, − which lie between 202 and 175 nm and result from excitation from the lone pair 5pπ (e) orbital of the iodine atom into the 6sa 1 Rydberg orbital. − In the C 3 v symmetry of the CH 3 I ground state, the removal of an electron from the highest occupied molecular orbital (e symmetry) results in 2 E 3/2 and 2 E 1/2 states that are split by approximately 0.6 eV as a result of the spin–orbit interaction . Coupling a 6sa 1 Rydberg electron to these ion core states results in five Rydberg states: the lower energy 3 E 2 and 3 E 1 states associated with the 2 E 3/2 core, and the 3 E 0 (A 1 ), 3 E 0 (A 2 ), and 1 E 1 states associated with the 2 E 1/2 core .…”

Determination of Spin−Orbit Branching Fractions in the Photodissociation of Halogenated Hydrocarbons

“…Historically, halogenated hydrocarbons have played an important role as prototypical systems for the study of photodissociation dynamics. − While many aspects of these systems have been investigated in substantial detail, one of the best studied observables has been the branching ratio between the two spin−orbit components of the ground state configuration of the halogen atom fragment following photoexcitation in the near-ultraviolet. In an early discussion of the near-ultraviolet absorption spectrum of the alkyl halides, Mulliken , showed that there were three optically allowed states based on excitation from the lone pair p orbital of the halogen to the lowest energy ns σ* orbital, and he labeled these 3 Q 0 , 1 Q 1 , and 3 Q 1 .…”

Photodissociation Dynamics of Small Molecules

“…The photolysis of CH 2 CO has been extensively studied (2,4 (48,49) have measured the 4.7 Um infrared emission of CO. The extent of the CO vibrational excitation can be estimated using a cold gas filter containing CO and a 4.7 pm filter.…”

“…Sulfur dioxide (2,4) and oxone are important atmospheric constituents. Particularly ozone acts as a radiation shield of sunlight below about 300 nm.…”

“…The photodissociation of ozone (2,4,20) in the ultraviolet region is important in atmospheric chemistry, since its main product, O( 1 D), reacts further with H 2 0 and N 2 0 to produce OH and NO (2). Recent studies (72-76) have shown that in the Hartley continuum (250-300 nm), 90% of the process is:…”