Metastable Decomposition of Ar3+ Cluster Ions Into Ar2+ and Ar+

Stephan, K.; Märk, T.D.; Märk, E.; Stamatovic, A.; Djurić, N.; Castleman, A. W.

doi:10.1002/ctpp.19830230404

Cited by 20 publications

(4 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The dimer fragmentation can be explained by simply counting the six available states of Ar2+,59 from which two are repulsive, leading immediately to Ar+. If we assume equal populations of the excited states, a fragmentation probability of 1:3 results, quite close to the experimental value 60. If this explanation is correct, systems with similar behaviordeep dimer ion well depths and shifted minimum distances compared with those of the neutral clusters-should show a similar fragmentation pattern.…”

supporting

confidence: 79%

Properties of neutral clusters from scattering experiments

Buck¹

1988

J. Phys. Chem.

119

View full text Add to dashboard Cite

Clusters of neutral atoms or molecules are usually generated as a distribution of different cluster sizes. This article describes the method of producing size-selected clusters by the momentum transfer in a scattering experiment. By measurement of the angular and velocity dependence of the scattered clusters in a crossed molecular beam experiment, the different species can be separated from each other. Applications of the method are presented for the collisional energy transfer of dimers, the formation and pressure dependence of weakly bound complexes in adiabatic expansions, and their fragmentation by electron impact ionization. The systems studied include atomic and molecular van der Waals clusters and quasi-hydrogen-bonded systems. In all cases large fragmentation is found which is caused by highly excited molecular ions which try to dispose of their excess enirgy by evaporation of single constituents or fast ion-molecule reactions within the cluster. Finally, results are presented for the infrared photodissociation of size-selected clusters which are internally "hot" or "cold" depending on whether the laser interaction takes place before or after the scattering process.

show abstract

supporting

confidence: 79%

Properties of neutral clusters from scattering experiments

Buck¹

1988

J. Phys. Chem.

119

View full text Add to dashboard Cite

show abstract

“…Lines drawn through the experimental points have been obtained from least-squares fits, and metastable fractions obtained by extrapolating to zero pressure are statistically significant nonzero values. dissociation rates obtained for Ar" cluster ions with n-A and 7<«<10 for fragmentations in the first field-free region [reaction (3)] and successive fragmentations in the first and second field-free region, respectively [i.e., reaction (7)]. Several conclusions and points follow from these data:…”

Section: 15mentioning

confidence: 84%

Observation of sequential decay series in metastable Ar clusters:Arn+→
Scheier
¹
,
Märk
²

1987
Phys. Rev. Lett.*
Self Cite
82
4
29
1
View full text Add to dashboard Cite

The first experimental observation of sequential decay of metastable cluster ions is reported herein. Ar cluster ions are produced by electron-impact ionization of a supersonic Ar cluster beam. Some of these ions are observed to decay via sequential decay series in the microsecond time scale, i.e., Ar" + *-• Ar"-i + * -Ar"-2 + * (with /7> 7), evaporating a single monomer in each of these successive decays. Conversely, the dominant metastable decay of Ar4 + *-*Ar2 + proceeds predominantly via a single-step fissioning process leading to the simultaneous evaporation of two neutral Ar monomers.PACS numbers: 36.40.+dRecently a number of studies have reported the metastable decay of singly and multiply charged cluster ions in the microsecond time regime. ] In most of these studies the evaporation loss of only one monomer was observed and investigated. l Although, several investigators have reported also the occurrence of metastable dissociations involving the loss of two monomers, 1 " 12 it was not possible in these studies to determine whether the observed loss of two monomers was simultaneous (singlestep fissioning process), i.e., Ar" + * -Ar"_ 2 + + 2Ar,or sequential (successive multiple evaporation), i.e.,Ar" + * -Ar"_ 1 + *-r-Ar kn-\,n-2 I * Ar"_ 2 + + Ar.(2)In order to gain more insight into the metastable dissociation mechanism and the concomitant evolution of cluster ion spectra, it is of great interest to answer this question (see discussions in Refs. 4-6, and 11).In this Letter we present direct experimental evidence that metastable argon cluster ions (produced by electron-impact ionization of a neutral-argon-cluster beam) which lose two monomers in the microsecond time-region decay via sequential decay series if their size is equal to or larger than Ar7 + . Conversely, the strong metastable decay of Ar4 + * into Ar2 + proceeds predominantly via a single-step fissioning process. These findings were made possible by the innovative use of a double-focusing sector field mass spectrometer (reversed geometry). We have also studied quantitatively the kinetics of these sequential decay series for cluster sizes including n =4 and 7<«< 10.The supersonic beam-electron impact ionization mass spectrometer system used has been described in detail previously. 6 In short, neutral argon clusters are produced by expanding neat Ar gas at --130°C and pressures up to -2.5 bars through a 20-/im nozzle. The ensuing supersonic beam passes a skimmer (differential pumping stage 6 ) and is crossed downstream at right angles by an electron beam of variable energy. Cluster ions thereby produced are (i) extracted at right angles from the ionization region, (ii) accelerated by an acceleration potential (typically to 1, 2, or 3 kV), analyzed in a 90° magnetic sector field followed by a 90° electric sector field, and (iii) detected with a CuBe conversion dynode followed by a channel electron multiplier.Essential to the present measurements (which go beyond the usual mass-to-charge analysis and simple metastable ion detection) is the existen...

show abstract

“…As mentioned before, the aim of the present study is to see, from realistic calculations, how competitive the RP channels could be in speeding up (or further slowing down) the lifetimes of the metastable cluster states observed experimentally. [8][9][10][11] This effect requires the knowledge of the diatomic energy content, i.e., the various asymptotic thresholds for the rotational levels populated after breakup, and furthermore the calculation of the bound states of the triatomic complex and of its metastable states. The actual RR potential energy surface will then provide the necessary coupling.…”

Section: Results From Quantum Dynamicsmentioning

confidence: 99%

“…6 In particular, the photodissociation of argon cluster ions by electron bombardment has provided a wide variety of data 7 on the possible electronic states involved and on the relative lifetimes of the observed photofragments. Moreover, Mark and co-workers 8 have demonstrated a while ago that small argon clusters comprised of as few as three atoms can display metastable decays in time regimes extending beyond 10 /-ts after the ionization event. Since it was also found that even the dimer ion 9 could display long-time metastability, it has been suggested that centrifugal effects could be responsible for such unusually long lifetimes 10 ,1l in the trimer clusters.…”

Section: Introductionmentioning

confidence: 99%

Competitive internal transfers in metastable decay of cluster ions

Buonomo¹,

Gianturco²,

Delgado‐Barrio

et al. 1994

The Journal of Chemical Physics

View full text Add to dashboard Cite

In a previous study of fragmentation patterns of (Ar)j clusters [G. Delgado-Barrio, S. Miret-Artes, P. Villarreal, and F. A. Gianturco, Z. Phys. D 27, 354 (1993)] it was found that overall rotations control the lifetimes of the occupied metastable states of the cluster and that a spherical, effective interaction was sufficient to describe the dynamical process. In the present study, the strong anisotropy of a more realistic three-particle interaction is introduced and its effects on metastable decay are examined. By separating internal rotations from internal vibrations of the diatomic ion, it is possible to show that internal predissociation pathways are very efficient and lead to very short lifetimes. The latter can be lengthened only when overall rotational states are directly included, thus confirming the physical picture of the earlier work.

show abstract

Metastable Decomposition of Ar₃⁺ Cluster Ions Into Ar₂⁺ and Ar⁺

Cited by 20 publications

References 14 publications

Properties of neutral clusters from scattering experiments

Properties of neutral clusters from scattering experiments

Observation of sequential decay series in metastable Ar clusters:Arn+→
Scheier
¹
,
Märk
²

1987
Phys. Rev. Lett.*
Self Cite
82
4
29
1
View full text Add to dashboard Cite

Competitive internal transfers in metastable decay of cluster ions

Contact Info

Product

Resources

About

Metastable Decomposition of Ar3+ Cluster Ions Into Ar2+ and Ar+

Cited by 20 publications

References 14 publications

Properties of neutral clusters from scattering experiments

Properties of neutral clusters from scattering experiments

Observation of sequential decay series in metastable Ar clusters:Arn+*→Scheier1, Märk2 1987Phys. Rev. Lett.Self Cite824291View full textAdd to dashboardCite

Competitive internal transfers in metastable decay of cluster ions

Contact Info

Product

Resources

About

Metastable Decomposition of Ar₃⁺ Cluster Ions Into Ar₂⁺ and Ar⁺

Observation of sequential decay series in metastable Ar clusters:Arn+→
Scheier
¹
,
Märk
²

1987
Phys. Rev. Lett.*
Self Cite
82
4
29
1
View full text Add to dashboard Cite