Rydberg and ion-pair states of HBr: New REMPI observations and analysis

Photofragmentation, state interaction, and energetics of Rydberg and ion-pair states: Resonance enhanced multiphoton ionization of HI

“…This typically shows as nonlinearity in plots of the energy level spacing ( E J ,J -1 = E(J ) -E(J -1)) vs. J . 16,[18][19][20] Regular patterns of rotational line positions are determined by transitions to regularly arranged rotational energy levels according to standard energy expressions for unperturbed states, depending on rotational (B v ) and centrifugal distortion (D v ) constants as well as on J quantum numbers. As an attempt to evaluate the spectroscopic constants, hence the unperturbed energy levels, as well as state interaction strengths (W ), from the observed data, simplified deperturbation calculations were performed.…”

“…18,20 These can involve one or more predissociating gateway states in which case the LW-effects also will depend on bound-to-bound state interactions. Thus ion-pair states, which do not predissociate easily, directly, [18][19][20] can show dramatic LW-effects due to interactions with one or more predissociating Rydberg states in which case the lifetime, hence the line-width, will depend on the Rydberg to ion-pair (bound-tobound) state interactions as well as predissociation processes of the Rydberg states. 20 Therefore, the rate of dissociation (1/τ 2 ) of an ion-pair vibrational state (2) has been expressed as a sum of terms, each of which is assumed to be a product of a predissociation rate (1/t 1i ) for a particular Rydberg state (1i) and a J dependent coupling rate (f 1i (J )) for the Rydberg to ion-pair state interaction, 20 i.e.,…”

“…5 The UV, VUV, and multiphoton excitation spectroscopy of these compounds is very rich in structure showing clearly resolved rotational bands due to excitation to Rydberg and ion-pair states. [6][7][8][9][10][11] Spectral perturbations showing as line shifts 7,8,10,[12][13][14][15][16][17][18][19][20] and/or as line intensity fluctuations 7,8,10,[12][13][14][15][16][17][18][19][21][22][23] are frequently observed as effects of state interactions and/or predissociation processes. 7-9, 12, 13, 18, 21 These are seen both in absorption 22,[24][25][26][27][28][29] and REMPI spectra.…”

“…21,34 Furthermore, perturbation effects have been shown to be valuable in spectral assignments. 19 The spectroscopy of the hydrogen halides has proven to highlight clearly the effects of various perturbation terms neglected in the Born-Oppenheimer (BO) approximation, particularly in the cases of interaction between electronically excited Rydberg states ( = 0, 1, 2, . .…”

“…18,20 A number of papers have been published, which place emphasis on state interactions, energy transfers, and photodissociation processes, in HCl 16,18,30,31,[35][36][37][38][39][40] and HBr. [18][19][20] Whereas most of the studies of hydrogen iodide (HI) have focused on the spectral assignments and the energetics of the Rydberg and ion-pair states, little emphasis has been placed on spectral perturbations for HI. Apart from statements concerning perturbation observations, 17,25,33 no detailed analyses of the spectral perturbations for HI have been reported.…”