Evidence for the existence of structures in gas-phase homomolecular clusters of water

Hermann, V.; Kay, Bruce D.; Castleman, A. W.

doi:10.1016/0301-0104(82)87079-1

Cited by 123 publications

(42 citation statements)

References 16 publications

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“…13 [42][43][44][45][46] These irregular intensity patterns have been supported for several different types of experiments. [14][15][16][17][18][19][20] Although the 26.5 eV photon energy is absorbed by a water cluster, no doubly charged species are apparent in the mass spectrum. Doubly charged water cluster ions are reported for large clusters ͑n Ͼ 37͒ using a multiphoton ͑800 nm͒ femtosecond ionization technique.…”

Section: Resultsmentioning

confidence: 99%

“…The two cluster ions ͑H 2 O͒ 21 H + and ͑H 2 O͒ 28 H + are identified as "magic number" clusters in this mass spectrum since intensity anomalies of the 21-mer and 28-mer are observed under numerous experimental conditions. [14][15][16][17][18][19] The structures of medium sized protonated water clusters have been reviewed by Chang et al recently. 20 Shiromaru et al 12 observed unprotonated ͑H 2 O͒ n + clusters ͑2 ഛ n ഛ 10͒ for the first time by applying near threshold photoionization with an Ar resonance lamp ͑11.83 eV͒ for a molecular beam expansion of H 2 O and Ar.…”

Section: Introductionmentioning

confidence: 99%

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Dynamics and fragmentation of van der Waals clusters: (H2O)n, (CH3OH)n, and (NH3)n upon ionization by a 26.5eV soft x-ray laser

Dong

Heinbuch

Rocca

et al. 2006

The Journal of Chemical Physics

102

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A tabletop soft x-ray laser is applied for the first time as a high energy photon source for chemical dynamics experiments in the study of water, methanol, and ammonia clusters through time of flight mass spectroscopy. The 26.5 eV/photon laser ͑pulse time duration of ϳ1 ns͒ is employed as a single photon ionization source for the detection of these clusters. Only a small fraction of the photon energy is deposited in the cluster for metastable dissociation of cluster ions, and most of it is removed by the ejected electron. Protonated water, methanol, and ammonia clusters dominate the cluster mass spectra. Unprotonated ammonia clusters are observed in the protonated cluster ion size range 2 ഛ n ഛ 22. The unimolecular dissociation rate constants for reactions involving loss of one neutral molecule are calculated to be ͑0.6-2.7͒ ϫ 10 4 , ͑3.6-6.0͒ ϫ 10 3 , and ͑0.8-2.0͒ ϫ 10 4 s −1 for the protonated water ͑9 ഛ n ഛ 24͒, methanol ͑5 ഛ n ഛ 10͒, and ammonia ͑5 ഛ n ഛ 18͒ clusters, respectively. The temperatures of the neutral clusters are estimated to be between 40 and 200 K for water clusters ͑10ഛ n ഛ 21͒, and 50-100 K for methanol clusters ͑6 ഛ n ഛ 10͒. Products with losses of up to five H atoms are observed in the mass spectrum of the neutral ammonia dimer. Large ammonia clusters ͑NH 3 ͒ n ͑n Ͼ 3͒ do not lose more than three H atoms in the photoionization/ photodissociation process. For all three cluster systems studied, single photon ionization with a 26.5 eV photon yields near threshold ionization. The temperature of these three cluster systems increases with increasing cluster size over the above-indicated ranges.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dynamics and fragmentation of van der Waals clusters: (H2O)n, (CH3OH)n, and (NH3)n upon ionization by a 26.5eV soft x-ray laser

Dong

Heinbuch

Rocca

et al. 2006

The Journal of Chemical Physics

102

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“…In other words, we assume that electron-impact induces the process ͑H 2 O͒ + m+2 → H 3 O + ͑H 2 O͒ m + OH. Previous studies using electron-impact ionization have shown that this is the dominant process in the gas phase, 7,8 but nevertheless the excess energy after ionization could induce some additional fragmentation such that the observed ion distribution becomes artificially skewed towards smaller clusters. In fact such fragmentation is known to occur to some extent even when water clusters are located in helium droplets, as shown in a spectroscopic and mass spectrometric study of water clusters by Fröchtenicht et al 9 The consequence of neglecting this ion fragmentation in calculating the helium droplet size is that the answer obtained will tend to underestimate the true average size.…”

Section: Droplet Size Survey Using Residual Water Vapormentioning

confidence: 96%

Controlled growth of helium nanodroplets from a pulsed source

Yang

Brereton

Ellis

2005

Review of Scientific Instruments

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Factors affecting the size of liquid-helium droplets produced by a pulsed nozzle are described. The shape of the nozzle orifice is found to be important in allowing control of the size of the droplets. With an appropriate choice of nozzle geometry, the average droplet size is shown to be continuously variable over nearly two orders of magnitude by adjustment of the helium gas stagnation pressure and/or temperature. A scaling law similar to, but not identical with, that found for helium droplets produced by continuous supersonic expansion sources is found for the pulsed source. The pulsed nozzle described in this article has been used to make helium droplets ranging in size from a few thousand atoms up to nearly 10 5 helium atoms.

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“…Interestingly the protonated (H20)2H + ion plays also an important role in the ion chemistry of the upper atmoshphere, since it has been shown that this species dominates the ion composition of the D region in the ionosphere [7]. Intensity anomalies observed in the mass spectra for the (H20)21H + and (H20)zsH + ions [3,8] have recently been attributed to metastable unimolecular decay of excited water clusters within a time window between about 4-40 ~s after the ionization process [2]. This latter investigation clearly shows that even for relatively long times after the ionization further decomposition processes of the hydrogen bonded species have to be taken into account.…”

Section: Introductionmentioning

confidence: 94%

Electron bombardment induced fragmentation of size selected neutral (D2O) n clusters

Buck¹,

Winter²

1994

Z Phys D - Atoms, Molecules and Clusters

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Abstract. The fragmentation behaviour of size selected neutral (D20)~ clusters with n<4 after ionization with 70 eV electrons is subject of this work. Size selection by scattering the cluster beam from a He target beam in combination with a quadrupole mass filter and time resolved measurements at specific laboratory angles enables us to determine the neutral precursor masses of the detected ions. The measured fragment pattern is dominated by deuterated ions of the form (D20),,_xD + with x > 1. The dimer fragmentation which leads with a probability of 62.5% to the D3 O+ ion and with 37.5% to D20 ÷ can be explained by fast intracluster ion-molecule reactions of charged monomer fragments reacting with the partner molecule. For larger clusters the fragmentation process can be rationalised by the creation of an initially highly excited D30+(DeO)x complex which is stabilized by evaporating additional monomer units with the main fragment channel (D20)D ÷ for n=3 and (D20)2D + for n=4. With increasing cluster size an increasing tendency of evaporation of more than one water monomer unit has been observed.

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Evidence for the existence of structures in gas-phase homomolecular clusters of water

Cited by 123 publications

References 16 publications

Dynamics and fragmentation of van der Waals clusters: (H2O)n, (CH3OH)n, and (NH3)n upon ionization by a 26.5eV soft x-ray laser

Dynamics and fragmentation of van der Waals clusters: (H2O)n, (CH3OH)n, and (NH3)n upon ionization by a 26.5eV soft x-ray laser

Controlled growth of helium nanodroplets from a pulsed source

Electron bombardment induced fragmentation of size selected neutral (D2O) n clusters

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