Photoabsorption and photodissociation cross sections of CO between 88.5 and 115 nm

Letzelter, C.; Eidelsberg, M.; Rostas, F.; Bretón, J.; Thieblemont, B.

doi:10.1016/0301-0104(87)80117-9

Cited by 134 publications

(83 citation statements)

References 34 publications

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“…Moreover, values for the lifetimes were obtained from experiments without rotational resolution. [2][3][4] In the present study we have shown that in the E 1 ⌸, vϭ1 state drastic rotational effects occur exactly in the range of J states that are populated in a room temperature sample (Jϭ5 -15). In this respect we wish to speculate on the question whether the higher predissociation yield of the vϭ1 state, with respect to vϭ0, may be attributed to accidental predissociation only.…”

Section: Discussionsupporting

confidence: 51%

“…1,2 The limits of the relevant wavelength range correspond to the ionization potential of atomic hydrogen and the first dissociation limit of CO ͑89 460 cm Ϫ1 ͒. Letzelter et al 3 established that the photodissociation mechanism does not involve direct excitation to a repulsive state, but rather occurs via absorption in rotationally resolved discrete bands which exhibit predissociation. In view of its astrophysical importance a number of detailed spectroscopic investigations on CO in the vuv range have been performed in recent years, by making use of classical spectrographs, 4,5 synchrotron sources [6][7][8] and laser sources.…”

Section: Introductionmentioning

confidence: 99%

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Accidental predissociation phenomena in theE 1Π,v=0 andv=1 states of 12C16O and 13C16O

Cacciani

Hogervorst

Ubachs

1995

The Journal of Chemical Physics

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We have studied vϭ0 and vϭ1 levels of the E 1 ⌸ state of CO in excitation from the ground state by one-and two-photon transitions, thus probing e and f ⌳-doublet components. New accidental predissociations were found in the E 1 ⌸, vϭ0 state for high J values ͑J e ϭ41, 44 for 12 C 16 O and J e ϭ41, 50 for 13 C 16 O͒. The predissociation phenomenon in the E 1 ⌸, vϭ1 state at Jϭ7 was reinvestigated and for both e and f components also Jϭ9, 10, and 12 were found to be perturbed. Perturbations by all three spin components of a k 3 ⌸, vϭ5 state were deduced. Furthermore the accidental predissociation in E 1 ⌸, vϭ0 J e ϭ31 was reinvestigated. Measurements of spectral line shifts were modeled assuming a spin-orbit coupling between E 1 ⌸ and the 3 ⌸ 1 component of the k 3 ⌸ state. Relative predissociation lifetimes of k 3 ⌸, vϭ3 and 5 with respect to E 1 ⌸, vϭ0 and vϭ1 are deduced from an analysis of observed intensity effects. For the E 1 ⌸, vϭ1 state rotational state dependent lifetimes were determined at low-J values. Line positions of CO lines were calibrated on an absolute frequency scale within 0.05 cm Ϫ1 against the tellurium and iodine standard in the visible. Accurate molecular constants for the E 1 ⌸, vϭ0 and vϭ1 states are determined for both 12 C 16 O and 13 C 16 O. The E 1 ⌸, vϭ1 state of 12 C 17 O is observed for the first time.

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Section: Discussionsupporting

confidence: 51%

Section: Introductionmentioning

confidence: 99%

Accidental predissociation phenomena in theE 1Π,v=0 andv=1 states of 12C16O and 13C16O

Cacciani

Hogervorst

Ubachs

1995

The Journal of Chemical Physics

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“…According to the models of van Dishoeck & Black (1988), the EÈX (0, 0) band plays an important role. Their modeling e †orts are based on the oscillator strengths of Letzelter et al (1987), later updated by Eidelsberg et al (1991). Recent experiments, including ours, indicate that the f-values of Eidelsberg et al for the strongest bands are too small, by nearly a factor of 2, for the EÈX (0, 0) band.…”

Section: Oscillator Strengthsmentioning

confidence: 83%

“…The discrepancy appears for f-values greater than about 6 ] 10~3. All other bands found to be important in the photodissociation process by van Dishoeck & Black have f-values greater than 7.5 ] 10~3, according to Letzelter et al (1987). We suspect that all these f-values have to be revised upward.…”

Section: Oscillator Strengthsmentioning

confidence: 85%

“…Essentially all decays from the upper states B and C (v@ \ 0) return the molecule to either the X or A state (Letzelter et al 1987 ;Kirby & Cooper 1989), with nearly all decays to ground involving vA \ 0. Experimental BÈX branching fractions span the range 0.56È0.68 (Dotchin, Chupp, & Pegg 1973 ;Letzelter et al 1987 ;Drabbels, Meerts, & ter Meulen 1993), indicating respective lifetimes of 17È20 ns when using our f-value. The early measurements summarized by Krishnakumar & Srivastava (1986) and those of Drabbels et al (1993) yielded lifetimes that are too long by one to several standard deviations.…”

Section: Radiative L Ifetimesmentioning

confidence: 99%

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Oscillator Strengths for B – X , C – X , and E – X Transitions in Carbon Monoxide

Federman

Fritts

Cheng

et al. 2001

ASTROPHYS J SUPPL S

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Band oscillator strengths for electronic transitions in CO were obtained at the Synchrotron Radiation Center of the University of WisconsinÈMadison. Our focus was on transitions observed in interstellar spectra with the Far-Ultraviolet Spectroscopic Explorer ; these transitions are also important in studies of selective isotope photodissociation, where fractionation among isotopomers can occur. Absorption from the ground state X 1&`(vA \ 0) to A 1% (v@ \ 5), B 1&`(v@ \ 0, 1), C 1&`(v@ \ 0, 1), and E 1% (v@ \ 0) was measured. Fits to the AÈX (5, 0) band, whose oscillator strength is well known, yielded the necessary column density and excitation temperature. These parameters were used in a least-squares Ðt of the observed proÐles to extract the band oscillator strengths of the transitions of interest. Our oscillator strengths are in excellent agreement with results from recent experiments using a variety of techniques. This agreement provides the basis for a self-consistent set of f-values at far-ultraviolet wavelengths for studies of interstellar (and stellar) CO.

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Precision Laser Spectroscopy in the Extreme Ultraviolet

Eikema

Ubachs

2011

Handbook of High‐resolution Spectroscopy

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Techniques for the production of short wavelengths in the extreme ultraviolet wavelength range are described, spanning low‐order harmonic generation in the perturbative regime for narrow bandwidth XUV production to the plateau‐regime with the three‐step collisional model for the generation of high harmonics with broadband ultrafast pulses. In addition, the intermediate regime is discussed for pulses of 300 ps duration, as well as the regime of harmonic conversion based on continuous wave lasers aiming at the production of coherent Lyman‐α radiation. Applications of XUV sources in the frequency domain typically rely on the production of XUV‐light from narrowband Fourier‐transform‐limited pulses for recording high‐resolution spectra. Alternatively, harmonically upconverted pulses of ultrashort duration (with inter‐pulse coherence) can be used for spectroscopic studies in the time and frequency domain (such as direct frequency comb spectroscopy techniques). Examples of both approaches for atomic and molecular spectroscopy are discussed at some length. For precision metrology on atomic systems, a focus is put on the Lamb shift determination in the He ground state. In the realm of molecular spectroscopy, predissociation phenomena in the nitrogen molecule are highlighted, with relevance for dissociation processes occurring in the upper layers of the Earth atmosphere. Similar predissociation phenomena in carbon monoxide are also treated in some detail, in this case with relevance for the chemistry in interstellar clouds. Precision XUV spectroscopy of molecular hydrogen is discussed as well, as it relates to the possibility of detecting a variation of the proton–electron mass ratio on a cosmological time scale. In the last section, applications of direct frequency comb spectroscopic techniques at short wavelengths are explained and prospects are given for using these techniques at extreme ultraviolet wavelengths.

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Photoabsorption and photodissociation cross sections of CO between 88.5 and 115 nm

Cited by 134 publications

References 34 publications

Accidental predissociation phenomena in theE 1Π,v=0 andv=1 states of 12C16O and 13C16O

Accidental predissociation phenomena in theE 1Π,v=0 andv=1 states of 12C16O and 13C16O

Oscillator Strengths for B – X , C – X , and E – X Transitions in Carbon Monoxide

Precision Laser Spectroscopy in the Extreme Ultraviolet

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