song_2010 ========= D\. Song, A\. Azarm, Y\. Kamali, K\. Liu, A\. Xia, Y\. Teranishi, S\.\-H\. Lin, F\. Kong and S\. L\. Chin, "Neutral Dissociation of Superexcited Oxygen Molecules in Intense Laser Fields", J\. Phys\. Chem\. A 114, 3087\-3095 \(2010\) `Source record `__ · :doc:`Catalogue ` · :doc:`Review register ` DOI: `10\.1021/jp907662z `__ **Source kind:** measurement **Recorded technique:** Fluorescence of excited O atoms from O2 in an intense field \(p\. 3088\)\: Ti\:sapphire CPA \(Spitfire\), 800 nm, transform\-limited 'about 42 fs at fwhm' \(single\-shot autocorrelator\), 1 kHz, up to 2 mJ, 5 mm beam \(1/e^2\), energy set by a half\-wave plate before the compressor; focused by an f = 100 cm lens into a chamber filled with 10 Torr of pure O2 \(background 4 x 10^\-2 Torr\)\. Side fluorescence imaged onto a SpectraPro 500i spectrometer \(1200 or 2400 groove/mm\) and a gated ICCD \(gate 500 ns, 50 ns after the pulse\)\. Pump\-probe fluorescence depletion\: an about 900 uJ 800 nm pump and an OPA probe at 1338 nm, about 50 fs, about 65 uJ, polarisation horizontal and parallel to the pump's, same lens; overlap checked by four\-wave mixing in air\. Calculations\: CASSCF/aug\-cc\-pVTZ excitation energies and dipoles of 96 valence states of O2 and multiphoton excitation probabilities \(42 fs, 800 nm; Fig\. 4b\); Morse curves for the superexcited Rydberg states; quasi\-classical trajectories \(section 3\.5\.1\)\. **Materials in structured entries:** O2 **Dataset quantities:** dissociation\_time **Contents:** 3 datasets; 0 formulas. Curation notes -------------- Journal pp\. 3087\-3095 = pdf pages 1\-9 \(J\. Phys\. Chem\. A 2010, 114, 3087; published on the web 12/31/2009; received 8 August 2009\)\. The library folder carries 2009, the online date; the record id takes the journal year, 2010\. Identity checked against pdf p\. 1\. Curated 2026\-10\-09 \(TC\-960\)\. THE PULSE AND INTENSITY\. 800 nm, about 42 fs FWHM; 'at the laser intensity of ~2 x 10^14 W/cm^2' \(abstract; 'in a strong laser field of 2 x 10^14 W/cm^2', p\. 3088\)\. The intensity calibration is not described\. Linear polarisation is implied for the pump \('The probe beam had a horizontal polarization parallel to that of the pump beam', p\. 3088\)\. PHOTON\-ORDER SLOPES \(no quantity holds an intensity exponent; reported, not taken\)\: 'Three slopes are obtained as 8\.9, 11\.1, and 11\.3 in a log\-log plot for the wavelengths of 615\.9, 777\.5, and 845\.0 nm, respectively \(Figure 4a\)', read as at least ten 800 nm photons, \>15\.5 eV, above the first ionisation potential 'of 12\.0697 eV' \(p\. 3089, no source\); the calculated excitation probabilities of the 96 states have slopes 'between 9 and 11' \(Fig\. 4b\)\. The intensity range of Fig\. 4a is not stated in the text\. The 777 nm signal is linear in pressure from 0\.1 to 10 Torr \('the slope is nearly 1', Fig\. 3\), so the emitters come from unimolecular dissociation \(p\. 3088\)\. THE TIMES \(datasets\)\: the fluorescence depletion at 777\.5 nm against pump\-probe delay \(Fig\. 8b\)\: 'The rise time of the depletion is about 50 fs, which is the order of the laser pulse width\. The decay lasts for 150 fs' \(p\. 3094\); 'The measured lifetime of 150 fs for the intermediate is consistent with predissociation mechanism' \(p\. 3094\)\. Other lines show 'roughly the same temporal width'\. The 150 fs is a width read from the depletion curve, not a fitted lifetime; no uncertainty\. The quasi\-classical trajectories on the O2\*\*\(\(O2\+ b 4Sigma\_g\-\) 4p pi\_u, 3Pi\_u\) Morse curve reach the crossing in 'about 100 fs'; 'if it was a direct dissociation, the dissociation period would be as long as about 600 fs predicted in a similar calculation' \(p\. 3093\)\. Autoionisation of n = 4 Rydberg molecules is estimated as 10^10 n^\-3 to 10^12 n^\-3 s^\-1, sub\-nanosecond \(p\. 3093; their ref\. 23\); not taken\. TABLE 1 \(pp\. 3090\-3091; tbl\_70f4477290cb, tbl\_a2059a5c3c11\) maps excitation\-energy bands \(15\.3\-17\.1, 17\.0\-18\.0, 19\.0\-21\.0 eV\) to optically excited and dissociating superexcited Rydberg states of O2, the products O\(3P\) \+ O\*\(n, l\) and their emission lines \(observed, and NIST's 'ref 20'\)\. It is an assignment, not a measured property of O2 that a quantity holds \(the atomic O lines are not optmat data, and O is not a registered material\); not extracted\. Thirty\-three lines are observed, ten not in NIST, and three new O Rydberg levels \(11s and 12s 5S0, 10d 5D0\) proposed \(p\. 3089\)\. The product threshold O\(3P\) \+ O\(Rydberg\) 'is at least 15 eV' \(p\. 3091\)\. The Morse parameters of section 3\.3\.2 are not tabulated\. FIGURES \(not digitised; raster images\)\: Fig\. 4a, the fluorescence of three lines against laser intensity \(log\-log\), whose slopes are printed; Fig\. 8b, the 777\.5 nm fluorescence depletion against delay; Fig\. 8a, the calculated trajectory probability against time\. The fluorescence is not a calibrated yield of all neutral O atoms \(the library's scope note\)\. **Recorded bibliographic identity status:** VALIDATED. This concerns identification of the source; it does not establish the scientific correctness of its contents. Datasets -------- song\_2010/depletion\_lifetime\_O2 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "depletion_lifetime_O2", "material": "O2", "table": "text", "quantity": "dissociation_time", "unit": "fs", "abscissa": "none", "use": "check", "uncertainty": { "level": "not stated" }, "parameters": { "channel": "O2** (superexcited) -> O(3P) + O(3p 5P), predissociation", "kind": "lifetime", "state": "superexcited Rydberg states of O2 converging to O2+ A, b or B, as assigned", "method": "fluorescence depletion by a delayed probe (pump 800 nm, probe 1338 nm)", "wavelength_nm": 800, "pulse_fs": 42, "polarization": "linear", "intensity_w_cm2": 200000000000000.0 } } 1 inline points in the source record. p\. 3094 \(Fig\. 8b\)\: 'The decay lasts for 150 fs'; 'The measured lifetime of 150 fs for the intermediate'\. The temporal width of the 777\.5 nm fluorescence depletion by a delayed 1338 nm, about 50 fs probe, read by the authors as the time the optically excited superexcited state takes to cross to the dissociating one \(predissociation\)\. An approximate width, not a fitted constant; the rise \(about 50 fs\) is the pulse\. No uncertainty\. 800 nm, about 42 fs pump at about 2 x 10^14 W/cm^2 \(the pump's intensity in the pump\-probe set\-up, about 900 uJ, is not stated separately\)\. song\_2010/qct\_predissociation\_O2 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "qct_predissociation_O2", "material": "O2", "table": "text", "quantity": "dissociation_time", "unit": "fs", "abscissa": "none", "use": "check", "uncertainty": { "level": "not stated" }, "parameters": { "channel": "O2**((O2+ b 4Sigma_g-) 4p pi_u, 3Pi_u) -> crossing to the dissociating superexcited curve", "kind": "calculated", "method": "quasi-classical trajectories on empirical Morse curves" } } 1 inline points in the source record. p\. 3093 \(Fig\. 8a\)\: the quasi\-classical trajectories on the Morse curve of O2\*\*\(\(O2\+ b 4Sigma\_g\-\) 4p pi\_u, 3Pi\_u\), started at 1\.21 A with zero mean velocity, reach the crossing with the dissociating curve in 'about 100 fs' \(the average moving time\)\. Morse curves built from the ion cores' constants and NIST atomic limits \(section 3\.3\.2\)\. No uncertainty\. song\_2010/qct\_direct\_O2 ~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "qct_direct_O2", "material": "O2", "table": "text", "quantity": "dissociation_time", "unit": "fs", "abscissa": "none", "use": "check", "uncertainty": { "level": "not stated" }, "parameters": { "channel": "O2** -> O(3P) + O*(Rydberg), direct dissociation (as the authors contrast it)", "kind": "calculated", "method": "quasi-classical trajectories ('a similar calculation')" } } 1 inline points in the source record. p\. 3093\: 'if it was a direct dissociation, the dissociation period would be as long as about 600 fs predicted in a similar calculation'\. The state and the details of that calculation are not given\. No uncertainty\. Formulas -------- No formulas are recorded. Corrections ----------- No dataset errata are recorded in this source record. Formula corrections, where recorded, appear with their formulas above. Curation notes may also discuss corrections or unresolved interpretation. Consult the :doc:`review register ` for the checks and decisions.