Michal HejdukCharles University in Prague | CUNI · Faculty of Mathematics and Physics
Michal Hejduk
PhD
Looking for collaborators in the glass-core microwave device manufacturing technology development.
About
40
Publications
3,611
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
327
Citations
Introduction
I am interested in ultracold interactions between ions and electrons in gas phase.
I am building a cryogenic radio-frequency trap, in which we will store laser-cooled ions with electrons.
Additional affiliations
February 2021 - present
Position
- Principal Investigator
Description
- Leading the research in ultra-cold plasma physics.
May 2020 - January 2021
Valeo autoklimatizace k.s.
Position
- Engineer
Description
- Developing new optical imaging technologies.
April 2017 - April 2020
Education
October 2009 - September 2013
Publications
Publications (40)
We report a simple and efficient two-step experimental procedure of glass metallization using laser microstructuring at ambient onditions. An adhesive pattern was created on the glass substrate using a laser, which imposes mechanical interlocking. An adhesive Cu layer was deposited on the glass substrate by magnetron sputtering and then electroplat...
Ultra-high vacuum conditions are ideal for the study of trapped ions. They offer an almost perturbation-free environment, where ions confined in traps can be studied for extended periods of time—facilitating precision measurements and allowing infrequent events to be observed. However, if one wishes to study processes involving molecular ions, it i...
We present experimental studies of reactions of doubly charged carbon cation (carbon dication, C2+, C iii) with O2, N2, CO, and HD molecules. A temperature-variable cryogenic linear 22-pole radio frequency ion trap was employed to obtain reaction rate coefficients and their temperature dependencies in the range from 40 to 300 K. The measured coeffi...
Radicals are prevalent in gas-phase environments such as the atmosphere, combustion systems, and the interstellar medium. To understand the properties of the processes occurring in these environments, it is helpful to study radical reaction systems in isolation-thereby avoiding competing reactions from impurities. There are very few methods for gen...
A new optical system is introduced for the imaging of Coulomb crystals held in a cryogenic ion trap where there are space limitations preventing the placement of an objective close to the fluorescing ions. The optical system features an off-axis parabolic (OAP) mirror relay microscope that will serve to acquire images of a lattice of fluorescing io...
In Zeeman deceleration, only a small subset of low-field-seeking particles in the incoming beam possess initial velocities and positions that place them within the phase-space acceptance of the device. In order to maximise the number of particles that are successfully decelerated to a selected final velocity, we seek to optimise the phase-space acc...
A Halbach array composed of 12 permanent magnets in a hexapole configuration is employed to deflect hydrogen atoms as they exit a Zeeman decelerator. The ability to preferentially manipulate H atoms is very useful, as there are currently very few techniques that are appropriate for purifying a beam of H atoms from precursor molecules (such as molec...
We present studies on the thermalisation of H3⁺ ions in a cold He/Ar/H2 plasma at temperatures 30 - 70 K. We show that we are able to generate a rotationally thermalised H3⁺ ensemble with a population of rotational and nuclear spin states corresponding to a particular ion translational temperature. By varying the para-H2 fraction used in the experi...
We study interactions between a strongly-coupled non-neutral crystallised plasma and slow neutral atoms or molecules in order to understand quantum mechanical effects governing ion-neutral reactions. We employ laser cooling to obtain ion ensembles with sub-Kelvin temperatures in a linear Paul trap. Neutral molecules are manipulated by decelerators...
We study interactions between a strongly-coupled non-neutral crystallised plasma and slow neutral atoms or molecules in order to understand quantum mechanical effects governing ion-neutral reactions. We employ laser cooling to obtain ion ensembles with sub-Kelvin temperatures in a linear Paul trap. Neutral molecules are manipulated by decelerators...
Outreach propagation of our research:
Many of us wonder where we, living beings, come from and how it happened that we are here. Science tries to explain this in various manners. I tend to look for answers in times when there was no solar system here, only a dark molecular cloud. Chemists and astronomers believe that many chemicals essential for li...
I studied low temperature phase transition of medium-sized negative water clusters (H2O)n-, n=50. Our hypothesis was that the clusters undergo glass transition. The way how to test this hypothesis was to vary a rate of cooling, i.e. the rate of relaxation of the internal structure. Precooling set-up was built but the project suffered from inability...
Detailed measurements employing a combination of a cryogenic flowing afterglow with Langmuir probe (Cryo-FALP II) and a stationary afterglow with near-infrared absorption spectroscopy (SA-CRDS) show that binary electron recombination of para-H3 (+) and ortho-H3 (+) ions occurs with significantly different rate coefficients, (p)αbin and (o)αbin, esp...
Rate coefficients for nuclear spin state-specific recombination of H3+ ions with thermal electrons were measured using FALP and SA techniques at temperatures 77–300 K. For this purpose H2 gas with both thermal and enriched population of the para nuclear spin configuration was used. Measurements have shown that at 77 K para-H3+ exhibits five times h...
Stationary afterglow measurements in conjunction with near-infrared absorption spectroscopy show that the recombination of the H-3(+) ion with electrons in ionized gas mixtures of He, Ar, and H-2 at 300 K is strongly enhanced by neutral helium and by molecular hydrogen. The H-2-assisted ternary recombination coefficient K-H2 = (8.7 +/- 1.5) x 10(-2...
Using a radiofrequency ion trap at low temperatures, an experimental study of collisions of N+ with or-tho/para-H2 is reported.
We studied how distribution of nuclear-spin states of H3+ ions or H2 molecules influence rate coefficients of H3+-electron recombination or reactions of H2 with N+ or H+, with regard to kinetic and internal temperatures of the reactants. Experiments were carried out in plasma environment or in an ensemble of ions in an ion trap. Main diagnostic met...
Ternary electron-assisted collisional radiative recombination (E-CRR) and neutral-assisted radiative recombination (N-CRR) have very strong negative temperature dependencies and hence dominate electron recombination in some plasmas at very low temperatures. However, there are only few data for molecular ions and almost none for atomic ions at tempe...
Using a low-temperature 22-pole ion trap apparatus, detailed measurements for the title reaction have been performed between 10 K and 100 K in order to get some state specific information about this fundamental hydrogen abstraction process. The relative population of the two lowest H2 rotational states, j = 0 and 1, has been varied systematically....
The results of an experimental study of the H3(+) and D3(+) ions recombination with electrons in afterglow plasmas in the temperature range 50-230 K are presented. A flowing afterglow apparatus equipped with a Langmuir probe was used to measure the evolution of the electron number density in the decaying plasma. The obtained values of the binary re...
We present results of plasma afterglow experiments on ternary electron-ion recombination rate coefficients of H3+ and D3+ ions at temperatures from 50 K to 300 K and compare them to possible three-body reaction mechanisms. Resonant electron capture into H3* Rydberg states is likely to be first step in the ternary recombination, rather than third-bo...
Recombination of D(3) (+) ions with electrons at low temperatures (80-130 K) was studied using spectroscopic determination of D(3) (+) ions density in afterglow plasmas. The use of cavity ring-down absorption spectroscopy enabled an in situ determination of the abundances of the ions in plasma and the translational and the rotational temperatures o...
Results of an experimental study of binary recombination of para- and ortho-H(3)(+) ions with electrons are presented. Near-infrared cavity-ring-down absorption spectroscopy was used to probe the lowest rotational states of H(3)(+) ions in the temperature range of 77-200 K in an H(3)(+)-dominated afterglow plasma. By changing the para/ortho abundan...
Rate coefficients for collisional radiative recombination (CRR) of
Ar+ ions with electrons were measured in a helium-buffered
flowing-afterglow (Cryo-FALP) experiment in temperature range 77-180 K
and at electron densities ne from 108 to
1010 cm-3. The measured ternary rate coefficient
KCRR at 77 K is (1.1 ± 0.4) × 10-17
cm6s-1 and the observed tem...
Measurements in H(3)(+) afterglow plasmas with spectroscopically determined relative abundances of H(3)(+) ions in the para-nuclear and ortho-nuclear spin states provide clear evidence that at low temperatures (77-200 K) para-H(3)(+) ions recombine significantly faster with electrons than ions in the ortho state, in agreement with a recent theoreti...
We have applied a continuous-wave near-infrared cavity ring-down spectroscopy method to study the parameters of a
-dominated plasma at temperatures in the range 77–200 K. We monitor populations of three rotational states of the ground vibrational state corresponding to para and ortho nuclear spin states in the discharge and the afterglow plasma in...
Results of an experimental study of binary recombination of para- and ortho- ${\rm{H}}_{\rm{3}}^{\rm{ + }}$ ions with electrons are presented. Near-infrared cavity-ring-down absorption spectroscopy was used to probe the lowest rotational states of ${\rm{H}}_{\rm{3}}^{\rm{ + }}$ ions in the temperature range of 77-200 K in an ${\rm{H}}_{\rm{3}}^{\rm...
Recombination of H3+ with electrons is a key process for many plasmatic environments. Recent experiments on storage ring devices used ion sources producing H3+ with enhanced populations of H3+ ions in the para nuclear spin configuration to shed light on the theoretically predicted faster recombination of para states. Although increased recombinatio...
Utilizing different ratios of para to ortho H₂ in normal and para enriched hydrogen, we varied the population of para-H₃⁺ in an H₃⁺ dominated plasma at 77 K. Absorption spectroscopy was used to measure the densities of the two lowest rotational states of H₃⁺. Monitoring plasma decays at different populations of para-H₃⁺ allowed us to determine the...
Measurements of recombination rate coefficients of binary and ternary recombination of and ions with electrons in a low temperature plasma are described. The experiments were carried out in the afterglow plasma in helium with a small admixture of Ar and parent gas (H2 or D2). For both ions a linear increase of measured apparent binary recombination...
Dissociative recombination of H3+ ions with electrons at temperatures
lower than 100 K is being studied intensively recently to confirm the theoretical prediction of a big difference between recombination rate coefficients of these ions in two lowest rotational levels (belonging to para and ortho nuclear spin states). In the present work, we invest...
We present a study of spin-dependent recombination of H 3 + ions with electrons at 77 K. A near infrared continuous wave cavity ring down spectrometer (cw-CRDS) was employed to obtain concentration evolutions of the two lowest rotational states of H 3 + , which have different nuclear spin (ortho and para). From the measured decrease of para-H 3 + a...
Reported is flowing afterglow (FALP) study of recombination of KrH+ and KrD+ ions with electrons at 250 K in mixtures of He/Kr/H2 and He/Kr/D2, respectively. The influence of fast recombining cluster ions formation on apparent effective recombination rate coefficients (αeff) was measured and used in data analysis. The obtained binary rate coefficie...
New advanced data analysis method for calculation of recombination rate coefficients from the decay of electron density during the afterglow (along the flow tube) in a Flowing Afterglow Langmuir Probe (FALP) experiment is presented. The method is advantageous for measurements of recombination rate coefficients of slowly recombining ions in conditio...
Experimental studies of Electron Energy Distribution Function (EEDF) in well-defined conditions in Flowing Afterglow plasma using Langmuir probe are reported. EEDF was measured in pure helium at medium pressures (1600 Pa) during late afterglow (35 to 95 ms after discharge) in nearly relaxed thermal plasma (Te ~ 300-600 K). The influence of fast ele...
Questions
Questions (3)
I am looking for a producer or a seller of copper plated glass wafers for making a microwave device. The copper thickness should be around 50 microns and the adhesion should be pretty good to survive repetitive cooling and heating cycles. It should be ultra-high vacuum compatible. I will need only few of them, on the order of 10. Diameter shall be less than 50 mm. Is there any such maker in Europe? So far, I have seen only research papers about the topic of making copper layers but they were pretty old. The industry seems to have adopted the glass wafers but I see no companies offering them... Any ideas about where to ask?
Is there a reason why nobody performed Doppler cooling of Y III (Y^{2+}) ions? It seems that transitions are similar to those in Ca+ ions (three level system). Y III ions could be produced by laser ablation, which was the method used for getting optical spectra of these ions in past.
I am thinking about putting a PCB with a SMD resistor chain on a surface cooled down to 20 K. While there are enough resistors that would survive such environment, I am not sure how many thermal cycles the connections between the resistors and the PCB can survive. Does anyone have a relevant experience?
