Heavy Rydberg states: large amplitude vibrations.

Extremely large vibrational amplitude (≈8700 a.u.) heavy Rydberg levels in the HH[combining macron]1Σ+g state, located only 25 cm-1 below the ion-pair dissociation limit, are reported.

Heavy Rydberg behaviour in high vibrational levels of some ion-pair states of the halogens and inter-halogens.

We report the identification of heavy Rydberg resonances in the ion-pair spectra of I2, Cl2, ICl, and IBr. Extensive vibrational progressions are analysed in terms of the energy dependence of the quantum defect δ(Eb) rather than as Dunham expansions. This is shown to define the heavy Rydberg region, providing a more revealing fit to the data with fewer coefficients and leads just as easily to numbering data sets separated by gaps in the observed vibrational progressions.

A combined resonance enhanced multiphoton ionization and ab initio study of the first absorption band of 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, and hexafluorobenzene.

The resonance enhanced multiphoton ionization (REMPI) spectra of jet-cooled penta- and hexafluorobenzene when excited in the region λ(ex) = 265-253 nm of the first absorption band and observed only in the CF(+) mass channel is dominated by rotational structure in the A←X transition of CF. However, structure in the CF(+) channel for λ(ex) > 265 nm is not a continuation of this CF spectrum and is assigned to vibrational activity in two low-frequency modes of a distorted excited state of the parent molecule. The vibrational structure is assigned to the lowest ππ* state from a comparison with the equivalent spectrum of 1,2,4,5-tetrafluorobenzene.

A critical re-assignment of the Rydberg states of iodomethane based on new polarization data.

2- and 3-photon excitation of components of the lower Rydberg states of iodomethane (CH3I) using linearly and circularly polarized light, followed by ionization with one more photon, is used to determine their molecular term symbol, Ω, values as well as quantum defects. These Ω values, together with a detailed theoretical analysis, require a re-assignment of the 7s and 8s states to various components of the 5d and 6d states, but there is evidence of (n+2)s∕nd hybridization in the pairs of Ω = 1 states. Predissociation sets in for all Rydberg states beyond 6d based on the ground ((2)Π(3∕2)) state of the core, but sharp autoionizing resonances based on the (2)Π(1∕2) core state are assigned to the 9s, 7d, and 5f states.

Efficient long-range collisional energy transfer between the E0(g)(+)(3P2) and D0(u)(+)(3P2) ion-pair states of I2, induced by H2O, observed using high-resolution Fourier transform emission spectroscopy.

Using high-resolution Fourier transform emission techniques, we have resolved rotational structure in the D0(u)(+)((3)P(2)) → X0(g)(+) emission following collisional transfer from the E0(g)(+)((3)P(2)) state in I(2). The P:R branch ratios in the E0(g)(+)((3)P(2)) → D0(u)(+)((3)P(2)) transfer are found to vary enormously with v(E) and v(D). We show that the observed intensities are all consistent with the transfer being dominated by long-range, near-resonant collisions with residual H(2)O.

Characterization of the potential minimum of the F '0(u)(+)(1D2) ion-pair state of Cl2 using (1 + 2') optical-optical double resonance excitation and mass-resolved ion detection.

Vibrational levels of the F(')0(u)(+)((1)D(2)), F0(u)(+)((3)P(0)), and D0(u)(+)((3)P(2)) ion-pair states of (35)Cl(2) and (35)Cl(37)Cl in the range 62,500-67,600 cm(-1) have been observed using (1 + 2(')) optical-optical double resonance excitation with mass-resolved ion detection. The strong F(')0(u)(+)((1)D(2))/F0(u)(+)((3)P(0)) coupling has been modelled by a coupled two-state calculation. An optimized fit of the experimental data used an F(')0(u)(+)((1)D(2)) state potential with a T(e) of 65,177 cm(-1) and an R(e) of ≈2.

Long-range collisional energy transfer between charge-transfer (ion-pair) states of I2, induced by H2O and I2(X).

Long-range (resonant) energy transfer, between g/u charge-transfer states of molecular iodine [i.e., f0(g) (+)((3)P(0))-->F0(u)(+)((3)P(0)) and E0(g)(+)((3)P(2))-->D0(u) (+)((3)P(2))], induced by collisions with H(2)O and I(2)(X) via multipole coupling, has been observed.

Amplified spontaneous emission and collisional transfer from the f0(g)+ ((3)P0) ion-pair state of I2.

The work presented here extends previous studies of amplified spontaneous emission (ASE) between ion-pair (charge-transfer) states of I(2) and shows that ASE can occur between states correlating with different states of the cation, namely, f0(g)(+)((3)P(0)) and D0(u)(+)((3)P(2)), despite the smaller transition dipole moment between them. A value of 0.34 e A is obtained for the transition dipole under experimental conditions where the f0(g)(+)((3)P(0))-->D0(u)(+)((3)P(2)) ASE is eliminated.

Evidence for Rydberg doorway states in photoion pair formation in bromomethane.

The vacuum ultraviolet laser-excited photoion-pair formation spectrum of CH 3Br has been measured under high resolution in the threshold region. The (2 + 1) and (3 + 1) resonance-enhanced multiphoton ionization spectra in the same energy region are also reported. By comparison of the spectra in this and a more extended region, resonances in the photoion-pair formation spectrum are assigned to p and f Rydberg states.

Characterization of a shallow-bound 0g+ valence state of I2 using emission from the D 0u+(3P2) and F' 0u+(1D2) ion-pair states populated by amplified spontaneous emission.

A range of vibrational levels of the D 0(u)(+)((3)P(2)) and F' 0(u)(+)((1)D(2)) ion-pair states of I(2) is shown to be easily generated by amplified spontaneous emission (ASE) from their more accessible partners, E 0(g)(+)((3)P(2)) and f' 0(g)(+)((1)D(2)), in sufficient concentration for dispersed fluorescence studies of the D 0(u)(+)((3)P(2)) --> 0(g)(+)(bb) and F' 0(u)(+)((1)D(2)) --> 0(g)(+)(bb) transitions to be carried out. T(0) (J = 49) of this shallow-bound 0(g)(+)(bb) valence state is unambiguously determined and an improved R(e) value of 3.952 +/- 0.

Observation of three weakly bound valence states of I2.

Structured emission in the gas phase to two weakly bound valence states that correlate with the third dissociation limit, I*(2P1/2)+I*(2P1/2), designated as (bb), from two third tier ion-pair states of I2 correlating with I-(1S0)+I+(1D2), the 1g(1D2), and F'0u+(1D2) states, has been observed for the first time. The 1u(bb) state is shown to be bound by 377+/-2 cm(-1) and molecular constants have been determined. Vibrational structure in the 0g+(bb) state could not be resolved but the spectrum is consistent with the state being bound by 435 cm(-1).

Collisional energy transfer in the intermediate states used for optical-optical double resonance excitation of ion-pair states in I2.

The optical-optical double resonance spectra of I(2) and I(2)-Xe mixtures at room temperature reported in the literature using a fixed-wavelength, broad band pump laser have now been recorded using a tuneable, narrow band source. We show that during the time of the overlapped laser pulses ( approximately 10 ns) and with 10-20 Torr of Xe there is widespread collisional energy transfer in the intermediate state and that this phenomenon offers an alternative explanation for the broad bands in the excitation spectrum, assigned to XeI(2) complexes by the authors of the earlier study (M. E.

Electric-field-induced g/u mixing of the E0g+(3P2) and D0u+(3P2) ion-pair states of jet-cooled I2 observed using optical triple resonance.

Electric-field-induced electronic state g/u mixing of nearly isoenergetic rovibrational levels of the E0g+(3P2) and D0u+(3P2) ion-pair states of I2 has been observed using optical triple resonance combined with resonance ionization. Detectable mixing with applied fields of 1 kV/cm occurs over a range of energy level separations of < or = 0.3 cm(-1).