ROTATIONAL AUTOIONIZATION DYNAMICS IN HIGH RYDBERG STATES OF NITROGEN
The decay dynamics of the high Rydberg states of N2 converging on the first few rotational levels (N+ = 0,1,2,3) of the ground vibronic X 2Σg+ (v+ = 0) state of the N2+ cation have been investigated by delayed pulsed field ionization (PFI) following two-photon enhanced (2+1′) three-photon excitation...
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| Format: | Journal article |
| Language: | English |
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1995
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| _version_ | 1797097531441676288 |
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| author | Merkt, F Mackenzie, S Softley, T |
| author_facet | Merkt, F Mackenzie, S Softley, T |
| author_sort | Merkt, F |
| collection | OXFORD |
| description | The decay dynamics of the high Rydberg states of N2 converging on the first few rotational levels (N+ = 0,1,2,3) of the ground vibronic X 2Σg+ (v+ = 0) state of the N2+ cation have been investigated by delayed pulsed field ionization (PFI) following two-photon enhanced (2+1′) three-photon excitation via the a″ 1Σg+ (v′ = 0) state of N2. The experiments were carried out in the presence of a weak homogeneous dc electric field and at typical ion densities of 200-2000 ions/mm3. All Rydberg states in the range of principal quantum number n = 140-200 exhibit extreme stability against autoionization and predissociation and some have lifetimes which exceed 30 μs. The decay of the highest Rydberg states beyond n = 200 is induced by external perturbations (field ionization and collisional ionization) and no Rydberg states beyond n = 350 can be observed by delayed PFI. The Rydberg states which converge on the N+ = 0 and 1 rotational levels of the ion, and which therefore are not subject to rotational autoionization, decay into neutral products (by a process presumed to be predissociation) in less than 7 μs in the range n<100. The importance of predissociation is greatly reduced beyond n = 100 and becomes negligible on our experimental timescale (30 μs) above n = 140. The decay of the Rydberg states converging on the N + = 2 and 3 rotational levels of the ion is more complex. Below n = 100, only 30%-40% of the Rydberg population decays by fast rotational autoionization whereas 60%-70% decays by predissociation. The importance of predissociation decreases rapidly above n = 100 and becomes negligible beyond n = 140. The decay by rotational autoionization can be observed at all n values but becomes noticeably slower beyond n = 100. In the range n = 140-200 it exhibits a marked biexponential decaying behavior with 30% of the population decaying within a few microseconds and 70% displaying long term stability (τ>30 μs). The branching between predissociation and autoionization is explained by the effect of the dc electric field which mixes strongly the optically accessible p Rydberg series with the high l manifold beyond n = 100. The long lifetimes observed experimentally indicate that ml mixing becomes important as soon as l mixing sets in. © 1995 American Institute of Physics. |
| first_indexed | 2024-03-07T04:56:52Z |
| format | Journal article |
| id | oxford-uuid:d6e5750c-096c-429b-bc54-9b5649e89339 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T04:56:52Z |
| publishDate | 1995 |
| record_format | dspace |
| spelling | oxford-uuid:d6e5750c-096c-429b-bc54-9b5649e893392022-03-27T08:37:00ZROTATIONAL AUTOIONIZATION DYNAMICS IN HIGH RYDBERG STATES OF NITROGENJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:d6e5750c-096c-429b-bc54-9b5649e89339EnglishSymplectic Elements at Oxford1995Merkt, FMackenzie, SSoftley, TThe decay dynamics of the high Rydberg states of N2 converging on the first few rotational levels (N+ = 0,1,2,3) of the ground vibronic X 2Σg+ (v+ = 0) state of the N2+ cation have been investigated by delayed pulsed field ionization (PFI) following two-photon enhanced (2+1′) three-photon excitation via the a″ 1Σg+ (v′ = 0) state of N2. The experiments were carried out in the presence of a weak homogeneous dc electric field and at typical ion densities of 200-2000 ions/mm3. All Rydberg states in the range of principal quantum number n = 140-200 exhibit extreme stability against autoionization and predissociation and some have lifetimes which exceed 30 μs. The decay of the highest Rydberg states beyond n = 200 is induced by external perturbations (field ionization and collisional ionization) and no Rydberg states beyond n = 350 can be observed by delayed PFI. The Rydberg states which converge on the N+ = 0 and 1 rotational levels of the ion, and which therefore are not subject to rotational autoionization, decay into neutral products (by a process presumed to be predissociation) in less than 7 μs in the range n<100. The importance of predissociation is greatly reduced beyond n = 100 and becomes negligible on our experimental timescale (30 μs) above n = 140. The decay of the Rydberg states converging on the N + = 2 and 3 rotational levels of the ion is more complex. Below n = 100, only 30%-40% of the Rydberg population decays by fast rotational autoionization whereas 60%-70% decays by predissociation. The importance of predissociation decreases rapidly above n = 100 and becomes negligible beyond n = 140. The decay by rotational autoionization can be observed at all n values but becomes noticeably slower beyond n = 100. In the range n = 140-200 it exhibits a marked biexponential decaying behavior with 30% of the population decaying within a few microseconds and 70% displaying long term stability (τ>30 μs). The branching between predissociation and autoionization is explained by the effect of the dc electric field which mixes strongly the optically accessible p Rydberg series with the high l manifold beyond n = 100. The long lifetimes observed experimentally indicate that ml mixing becomes important as soon as l mixing sets in. © 1995 American Institute of Physics. |
| spellingShingle | Merkt, F Mackenzie, S Softley, T ROTATIONAL AUTOIONIZATION DYNAMICS IN HIGH RYDBERG STATES OF NITROGEN |
| title | ROTATIONAL AUTOIONIZATION DYNAMICS IN HIGH RYDBERG STATES OF NITROGEN |
| title_full | ROTATIONAL AUTOIONIZATION DYNAMICS IN HIGH RYDBERG STATES OF NITROGEN |
| title_fullStr | ROTATIONAL AUTOIONIZATION DYNAMICS IN HIGH RYDBERG STATES OF NITROGEN |
| title_full_unstemmed | ROTATIONAL AUTOIONIZATION DYNAMICS IN HIGH RYDBERG STATES OF NITROGEN |
| title_short | ROTATIONAL AUTOIONIZATION DYNAMICS IN HIGH RYDBERG STATES OF NITROGEN |
| title_sort | rotational autoionization dynamics in high rydberg states of nitrogen |
| work_keys_str_mv | AT merktf rotationalautoionizationdynamicsinhighrydbergstatesofnitrogen AT mackenzies rotationalautoionizationdynamicsinhighrydbergstatesofnitrogen AT softleyt rotationalautoionizationdynamicsinhighrydbergstatesofnitrogen |