Related Experiment Video
Updated: Dec 29, 2025

Methanol Independent Expression by Pichia Pastoris Employing De-repression Technologies
Published on: January 23, 2019
Strong-field control of H3 + production from methanol dications: Selecting between local and extended formation
Naoki Iwamoto1, Charles J Schwartz1, Bethany Jochim2
1Department of Physics, Augustana University, Sioux Falls, South Dakota 57197, USA.
Abstract:
Using the CD3OH isotopologue of methanol, the ratio of D2H+ to D3 + formation is manipulated by changing the characteristics of the intense femtosecond laser pulse. Detection of D2H+ indicates a formation process involving two hydrogen atoms from the methyl side of the molecule and a proton from the hydroxyl side, while detection of D3 + indicates local formation involving only the methyl group. Both mechanisms are thought to involve a neutral D2 moiety. An adaptive control strategy that employs image-based feedback to guide the learning algorithm results in an enhancement of the D2H+/D3 + ratio by a factor of approximately two. The optimized pulses have secondary structures 110-210 fs after the main pulse and result in photofragments that have different kinetic energy release distributions than those produced from near transform limited pulses. Systematic changes to the linear chirp and higher order dispersion terms of the laser pulse are compared to the results obtained with the optimized pulse shapes.
Related Concept Videos
Electrophilic Addition of HX to 1,3-Butadiene: Thermodynamic vs Kinetic Control
Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
Regioselectivity and Stereochemistry of Hydroboration
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Regioselective Formation of Enolates
Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
π Electron Effects on Chemical Shift: Overview

