Two-photon photodissociation dynamics of state-selected NO2

Abstract

Quantum. st~tes of N0 2 are selected. and then photodissociated by resonant two-photon photoexcItatlOn. The total photolYSIS energy is scanned over a region from 50 cm -1 below to 300. cm-I abov~ the threshold for ~roduction ofNO(X 2 n) + O(ID). This channel yielding eX~Ited ~xygen IS observed to domInate the production of vibrational ground state NO. ~I~tO~IC product J an~ A ~oublet state distributions are probed by resonant two-photon lOnIzatIon. The photodIssocIation cross section for production of specific NO quantum states is found to be structured in the photolysis wavelength. This structure is assigned to intermediate resonance in the two-phot?n photolysis. Rotational structure is identified in this pattern, and confirmed by separate optIcal-UV -double resonance spectroscopy using the same intermediate states i~ co~b~nation wit~ levels of the 3pu 2l:u+ Rydberg state of N0 2 • Though p~otodIsSOCIatIOn dynamIcs are found to be a very sensitive function of photolysis wavelength, dIfferent wavelengths that promote different transitions through the same intermediate state yield very similar dynamics. The existence and apparent patterns of photoselection in the product state dynamics are discussed in the light of recent theoretical developments incorporating electronic degrees of freedom in state-to-state photofragmentation.

Excited state wavepacket dynamics in NO2 probed by strong-field ionization

“…The production of both NO + and O + due to ionization of free neutral photofragments giving rise to the features observed at <100 fs can be ruled out, since these ion signals rapidly decay after reaching a maximum. Since free neutral dissociation products cannot vanish once formed, ionization of neutral photofragments would yield a signal which would increase asymptotically and then effectively remain constant out to very long time delays [26,27,40], in contrast to what was observed in our data.…”

“…TheD 2 B 2 state is expected to predissociate within 100 fs [58] via one of two dissociation thresholds, producing either NO( 2 Π) + O( 1 D) (the second dissociation limit at 5.08 eV) or NO( 2 Π) + O( 3 P) (the first dissociation limit at 3.11 eV, see Fig. 9) [27,59]. The production of both NO + and O + due to ionization of free neutral photofragments giving rise to the features observed at <100 fs can be ruled out, since these ion signals rapidly decay after reaching a maximum.…”

“…The NO 2 molecule is an exemplary system with which to study strong-field probing of photoexcited polyatomic molecules due the presence of non-adiabatic couplings between electronic states, intramolecular vibrational en- ergy redistribution (IVR) and neutral dissociation pathways. The literature associated with this system is extensive in both the frequency [24][25][26][27][28][29][30][31][32] and time domains [8][9][10][33][34][35][36][37][38][39] and hence adds to the suitability of NO 2 as an important system for studying the nature of pump-SFI probe spectroscopies in polyatomics. The photodynamics of NO 2 have been reviewed and summarised by Wilkinson and Whitaker [40].…”

Near threshold channel selective photodissociation of NO2

“…Interestingly, a similar propensity for the total parity of NO products has been observed by Bigio and Grant in two-photon photodissociation of NO2 into NO(X) +O(1D) [10]. In their experiment the process also started from jet-cooled NO2 with only " + " parity levels populated in the electronic ground state.…”

Simultaneous Measurement of Nitric Oxide (NO) and Nitrogen Dioxide (NO2) in Simulated Automobile Exhaust Using Medium Pressure Ionization—Mass Spectrometry

“…31 The species NO 2 has been measured using twocolor REMPI via (1þ1 0 ). 32 A single-color photoionization scheme has been developed to measure NO and NO 2 within engine exhaust using 230 nm light. 33 NO þ resulting from photoionization of NO 2 has a large initial kinetic energy distribution, leading to a broader peak than NO þ formed from photoionization of NO.…”