Image via World Wildlife Fund.
For some years now, many scientists have recognized that humanity has become so prevalent and powerful on Earth that we’re now globally affecting the geologic record, the actual rock record used by geologists to divide the past into named blocks. A year ago, a group of experts recommended that we should officially consider re-naming our geologic epoch the Anthropocene, meaning the Age of Humans. At the same time, scientists who look beyond Earth long spoken of a classification scheme for hypothetical extraterrestrial civilizations, named the Kardashev scale in 1964 for Soviet astronomer Nikolai Kardashev. And now a team of researchers has devised a new classification scheme. It’s reminiscent of the Kardashev scale because it could relate to other worlds in our Milky Way galaxy. And it’s reminiscent of the idea of an Anthropocene because it focuses in part on a civilization’s unintentional planetary impacts, much like those happening on Earth today.
The new paper is called Earth as a Hybrid Planet: The Anthropocene in an Evolutionary Astrobiological Context, and it’s published in the September 6, 2017 issue of the peer-reviewed journal Anthropocene (request text here). Lead author is Adam Frank, a professor of physics and astronomy at the University of Rochester.
The Kardashev scale focuses on a civilization’s intentional energy harvesting. Earth doesn’t rank even as a Type I civilization on this scale, that is, a civilization able to manipulate all the energy resources of its home planet. A Type II civilization can use all the energy in its solar system system. A super-advanced Type III civilization on the Kardashev scale can, theoretically, harness all the energy of its entire home galaxy.
The new system proposed by Frank and others is less about super advanced civilizations and more about life’s impact on its world, over time.
An early nuclear test at Bikini Atoll, 1946. When experts met in 2016 – and recommended officially considering re-naming our geologic epoch the Anthropocene – some felt the start of the Anthropocene should coincide with the beginning of nuclear bomb testing, which caused radioactive elements to be dispersed across Earth and thus laid down in the geologic record. Other experts pointed to other ongoing signs of the Age of Humans, which will also ultimately find their way into the rock record, including plastic pollution, soot from power stations, aluminium and concrete particles and high levels of nitrogen and phosphate in soils, derived from artificial fertilizers. Image via U.S. Dept. of Energy.
Here are the categories in the proposed new system:
Class I represents worlds with no atmosphere at all, such as the planet Mercury and the Earth’s moon.
Class II planets have a thin atmosphere containing greenhouse gases, but no current life, such as the current states of planets Mars and Venus.
Class III planets have perhaps a thin biosphere and some biotic activity, but much too little to “affect planetary drivers and alter the evolutionary state of the planet as a whole.” No current examples exist in the solar system, but early Earth might have represented such a world — and possibly early Mars, if life ever flickered there in the distant past.
Class IV planets have a thick biosphere sustained by photosynthetic activity and life has begun strongly affecting the planetary energy flow. In this system, Earth is a Class IV planet, the only one we currently know for certain exists. What do the scientists mean by energy flow? They’re talking about a state of non-equilibrium thermodynamics — a planet’s energy flow being out of synch – in a way that the presence of a technological civilization can cause.
Class V planets are the final stage in this system, with the planets profoundly affected by the activity of an advanced, energy-intensive species.
These phrases will occur more often in the coming years #Anthropocene #ClimateChangeIsReal #ExtremeWeather https://t.co/wN6tMKdIkm
— Ratn Sanjay, IPS (@ratnsanjayips) September 12, 2017
The new classification system, the researchers said, is a way of thinking about human sustainability on a planetary scale in the newly recognized Anthropocene epoch. They said:
Our premise is that Earth’s entry into the Anthropocene represents what might, from an astrobiological perspective, be a predictable planetary transition. We explore this problem from the perspective of our own solar system and exoplanet studies.
In our perspective, the beginning of the Anthropocene can be seen as the onset of the hybridization of the planet, a transitional stage from one class of planetary systems to another.
… Any world hosting a long-lived energy-intensive civilization must share at least some similarities in terms of the thermodynamic properties of the planetary system. Understanding these properties, even in the broadest outlines, can help us understand which direction we must aim our efforts in developing a sustainable human civilization.
In other words, they added:
If one does not know where one is going, it’s hard to get there.
Read more via University of Washington
View larger. | Is our current phase of civilization a step along a road to a Karashev-type world? Here’s an artist’s concept of the activities of a Kardashev Type III civilization. Such a civilization would encapsulate the energy of stars by so-called Dyson spheres or swarms. Image via Danielle Futselaar / ASTRON.
Bottom line: The Kardashev scale meets the Anthropocene in a newly proposed classification system. The system offers a new way of thinking about human sustainability on Earth.
Image via World Wildlife Fund.
For some years now, many scientists have recognized that humanity has become so prevalent and powerful on Earth that we’re now globally affecting the geologic record, the actual rock record used by geologists to divide the past into named blocks. A year ago, a group of experts recommended that we should officially consider re-naming our geologic epoch the Anthropocene, meaning the Age of Humans. At the same time, scientists who look beyond Earth long spoken of a classification scheme for hypothetical extraterrestrial civilizations, named the Kardashev scale in 1964 for Soviet astronomer Nikolai Kardashev. And now a team of researchers has devised a new classification scheme. It’s reminiscent of the Kardashev scale because it could relate to other worlds in our Milky Way galaxy. And it’s reminiscent of the idea of an Anthropocene because it focuses in part on a civilization’s unintentional planetary impacts, much like those happening on Earth today.
The new paper is called Earth as a Hybrid Planet: The Anthropocene in an Evolutionary Astrobiological Context, and it’s published in the September 6, 2017 issue of the peer-reviewed journal Anthropocene (request text here). Lead author is Adam Frank, a professor of physics and astronomy at the University of Rochester.
The Kardashev scale focuses on a civilization’s intentional energy harvesting. Earth doesn’t rank even as a Type I civilization on this scale, that is, a civilization able to manipulate all the energy resources of its home planet. A Type II civilization can use all the energy in its solar system system. A super-advanced Type III civilization on the Kardashev scale can, theoretically, harness all the energy of its entire home galaxy.
The new system proposed by Frank and others is less about super advanced civilizations and more about life’s impact on its world, over time.
An early nuclear test at Bikini Atoll, 1946. When experts met in 2016 – and recommended officially considering re-naming our geologic epoch the Anthropocene – some felt the start of the Anthropocene should coincide with the beginning of nuclear bomb testing, which caused radioactive elements to be dispersed across Earth and thus laid down in the geologic record. Other experts pointed to other ongoing signs of the Age of Humans, which will also ultimately find their way into the rock record, including plastic pollution, soot from power stations, aluminium and concrete particles and high levels of nitrogen and phosphate in soils, derived from artificial fertilizers. Image via U.S. Dept. of Energy.
Here are the categories in the proposed new system:
Class I represents worlds with no atmosphere at all, such as the planet Mercury and the Earth’s moon.
Class II planets have a thin atmosphere containing greenhouse gases, but no current life, such as the current states of planets Mars and Venus.
Class III planets have perhaps a thin biosphere and some biotic activity, but much too little to “affect planetary drivers and alter the evolutionary state of the planet as a whole.” No current examples exist in the solar system, but early Earth might have represented such a world — and possibly early Mars, if life ever flickered there in the distant past.
Class IV planets have a thick biosphere sustained by photosynthetic activity and life has begun strongly affecting the planetary energy flow. In this system, Earth is a Class IV planet, the only one we currently know for certain exists. What do the scientists mean by energy flow? They’re talking about a state of non-equilibrium thermodynamics — a planet’s energy flow being out of synch – in a way that the presence of a technological civilization can cause.
Class V planets are the final stage in this system, with the planets profoundly affected by the activity of an advanced, energy-intensive species.
These phrases will occur more often in the coming years #Anthropocene #ClimateChangeIsReal #ExtremeWeather https://t.co/wN6tMKdIkm
— Ratn Sanjay, IPS (@ratnsanjayips) September 12, 2017
The new classification system, the researchers said, is a way of thinking about human sustainability on a planetary scale in the newly recognized Anthropocene epoch. They said:
Our premise is that Earth’s entry into the Anthropocene represents what might, from an astrobiological perspective, be a predictable planetary transition. We explore this problem from the perspective of our own solar system and exoplanet studies.
In our perspective, the beginning of the Anthropocene can be seen as the onset of the hybridization of the planet, a transitional stage from one class of planetary systems to another.
… Any world hosting a long-lived energy-intensive civilization must share at least some similarities in terms of the thermodynamic properties of the planetary system. Understanding these properties, even in the broadest outlines, can help us understand which direction we must aim our efforts in developing a sustainable human civilization.
In other words, they added:
If one does not know where one is going, it’s hard to get there.
Read more via University of Washington
View larger. | Is our current phase of civilization a step along a road to a Karashev-type world? Here’s an artist’s concept of the activities of a Kardashev Type III civilization. Such a civilization would encapsulate the energy of stars by so-called Dyson spheres or swarms. Image via Danielle Futselaar / ASTRON.
Bottom line: The Kardashev scale meets the Anthropocene in a newly proposed classification system. The system offers a new way of thinking about human sustainability on Earth.
The bright flash on the right side of the sun is the X8.2-class flare, captured on September 10, 2017. The image shows a combination of wavelengths of extreme ultraviolet light that highlights the extremely hot material in flares, which has then been colorized. Image via NASA’s Solar Dynamics Observatory.
There were X-flares on the sun last week, and the same Active Region on the sun – AR2673 – again emitted an X-flare on September 10, 2017 as it was rotating out of our earthly view, due to the sun’s spin on its axis. NASA said:
The sun emitted a significant solar flare, peaking at 12:06 p.m. EDT on Sept. 10, 2017 (16:06 UTC). NASA’s Solar Dynamics Observatory, which watches the sun constantly, captured an image of the event. Solar flares are powerful bursts of radiation. Harmful radiation from a flare cannot pass through Earth’s atmosphere to physically affect humans on the ground, however — when intense enough — they can disturb the atmosphere in the layer where GPS and communications signals travel.
To see how this event may affect Earth, please visit NOAA’s Space Weather Prediction Center at spaceweather.gov, the U.S. government’s official source for space weather forecasts, alerts, watches and warnings.
This flare is classified as an X8.2-class flare. X-class denotes the most intense flares, while the number provides more information about its strength. An X2 is twice as intense as an X1, an X3 is three times as intense, etc.
This flare is the capstone on a series of flares from Active Region 2673, which was identified on Aug. 29 and is currently rotating off the front of the sun as part of our star’s normal rotation.
September 10, 2017 X-flare, via NASA SDO.
Bottom line: An X8.2-class flare, captured on September 10, 2017, from Active Region 2673. This region on the sun has now rotated out of our view.
The bright flash on the right side of the sun is the X8.2-class flare, captured on September 10, 2017. The image shows a combination of wavelengths of extreme ultraviolet light that highlights the extremely hot material in flares, which has then been colorized. Image via NASA’s Solar Dynamics Observatory.
There were X-flares on the sun last week, and the same Active Region on the sun – AR2673 – again emitted an X-flare on September 10, 2017 as it was rotating out of our earthly view, due to the sun’s spin on its axis. NASA said:
The sun emitted a significant solar flare, peaking at 12:06 p.m. EDT on Sept. 10, 2017 (16:06 UTC). NASA’s Solar Dynamics Observatory, which watches the sun constantly, captured an image of the event. Solar flares are powerful bursts of radiation. Harmful radiation from a flare cannot pass through Earth’s atmosphere to physically affect humans on the ground, however — when intense enough — they can disturb the atmosphere in the layer where GPS and communications signals travel.
To see how this event may affect Earth, please visit NOAA’s Space Weather Prediction Center at spaceweather.gov, the U.S. government’s official source for space weather forecasts, alerts, watches and warnings.
This flare is classified as an X8.2-class flare. X-class denotes the most intense flares, while the number provides more information about its strength. An X2 is twice as intense as an X1, an X3 is three times as intense, etc.
This flare is the capstone on a series of flares from Active Region 2673, which was identified on Aug. 29 and is currently rotating off the front of the sun as part of our star’s normal rotation.
September 10, 2017 X-flare, via NASA SDO.
Bottom line: An X8.2-class flare, captured on September 10, 2017, from Active Region 2673. This region on the sun has now rotated out of our view.
The moon rising on September 11, 2017 via Gowri Lakshminarayanan in Jersey City, New Jersey. He wrote: “This is a 21-image composite of the rising waning gibbous moon (~63%) over the Freedom Tower in New York. I’ve done many composites in the past, but this one is really special to me, and I made it as a mark of respect for those innocent lives lost 16 years back and to express my solidarity towards the people of New York and USA.”
The moon rising on September 11, 2017 via Gowri Lakshminarayanan in Jersey City, New Jersey. He wrote: “This is a 21-image composite of the rising waning gibbous moon (~63%) over the Freedom Tower in New York. I’ve done many composites in the past, but this one is really special to me, and I made it as a mark of respect for those innocent lives lost 16 years back and to express my solidarity towards the people of New York and USA.”
Tonight, find the large spiral galaxy next door. As shown on the chart at the top of this post, the Great Square of Pegasus serves as a great jumping off point for finding the Andromeda galaxy, otherwise known as M31. It sparkles over your eastern horizon at nightfall and travels westward across the sky throughout the night. For some idea of the Great Square’s size, extend your hand an arm’s length from your eye. You’ll see that any two Great Square stars are farther apart than the width of your hand.
As seen from mid-northern latitudes, the Square of Pegasus looks like a baseball diamond whenever it resides in the eastern sky. Imagine the farthest star to the left – Alpheratz – as the third-base star. An imaginary line drawn from the first-base star through Alpheratz points in the general direction of the Andromeda galaxy.
The Andromeda galaxy and two satellite galaxies as seen through a powerful telescope. To the eye, the galaxy looks like a fuzzy patch. It’s an island of stars in space, much like our Milky Way. Image Credit: NOAO
If it’s dark enough, you’ll see two streamers of stars flying to the north (or left) of the star Alpheratz. To some people, this grouping of stars looks like a bugle or a cornucopia. Along the bottom streamer, star-hop from Alpheratz to the star Mirach. Draw an imaginary line from Mirach through the upper streamer star (Mu Andromedae), and go twice the distance. You’ve just located the Andromeda galaxy!
If you can’t see this fuzzy patch of light with the unaided eye, maybe your sky isn’t dark enough. Try binoculars! Or try going to darker sky.
Read more: Andromeda galaxy, closest spiral to Milky Way
Enjoying EarthSky so far? Sign up for our free daily newsletter today!
View larger. | The Andromeda galaxy (right side of photo) as seen by EarthSky Facebook friend Ted Van at a Montana campsite in mid-August 2012. Thank you, Ted!
Bottom line: If you can find the Great Square of Pegasus, then you can star-hop to the Andromeda galaxy.
Donate: Your support means the world to us
Astronomy events, star parties, festivals, workshops for September-December, 2015
Super Blood Moon eclipse on night of September 27-28
Tonight, find the large spiral galaxy next door. As shown on the chart at the top of this post, the Great Square of Pegasus serves as a great jumping off point for finding the Andromeda galaxy, otherwise known as M31. It sparkles over your eastern horizon at nightfall and travels westward across the sky throughout the night. For some idea of the Great Square’s size, extend your hand an arm’s length from your eye. You’ll see that any two Great Square stars are farther apart than the width of your hand.
As seen from mid-northern latitudes, the Square of Pegasus looks like a baseball diamond whenever it resides in the eastern sky. Imagine the farthest star to the left – Alpheratz – as the third-base star. An imaginary line drawn from the first-base star through Alpheratz points in the general direction of the Andromeda galaxy.
The Andromeda galaxy and two satellite galaxies as seen through a powerful telescope. To the eye, the galaxy looks like a fuzzy patch. It’s an island of stars in space, much like our Milky Way. Image Credit: NOAO
If it’s dark enough, you’ll see two streamers of stars flying to the north (or left) of the star Alpheratz. To some people, this grouping of stars looks like a bugle or a cornucopia. Along the bottom streamer, star-hop from Alpheratz to the star Mirach. Draw an imaginary line from Mirach through the upper streamer star (Mu Andromedae), and go twice the distance. You’ve just located the Andromeda galaxy!
If you can’t see this fuzzy patch of light with the unaided eye, maybe your sky isn’t dark enough. Try binoculars! Or try going to darker sky.
Read more: Andromeda galaxy, closest spiral to Milky Way
Enjoying EarthSky so far? Sign up for our free daily newsletter today!
View larger. | The Andromeda galaxy (right side of photo) as seen by EarthSky Facebook friend Ted Van at a Montana campsite in mid-August 2012. Thank you, Ted!
Bottom line: If you can find the Great Square of Pegasus, then you can star-hop to the Andromeda galaxy.
Donate: Your support means the world to us
Astronomy events, star parties, festivals, workshops for September-December, 2015
Super Blood Moon eclipse on night of September 27-28
Artist’s concept of Cassini spacecraft making its final, distant flyby of Saturn’s moon Titan on September 11 Image via NASA/JPL-Caltech.
The Cassini spacecraft at Saturn made a final, distant flyby of the large moon Titan today (September 11, 2017). Mission engineers have been informally referring to this encounter as the goodbye kiss, because, as it occurs, Titan provides Cassini with a gravitational nudge that sends the spacecraft toward its dramatic ending in Saturn’s upper atmosphere this Friday, September 15. NASA said the Titan flyby went as planned today. The spacecraft made its closest approach to Titan at 19:04 UTC (3:04 p.m. EDT; translate to your time zone), at an altitude of 73,974 miles (119,049 km) above the moon’s surface.
Cassini is scheduled to make contact with Earth on September 12, at which time images and other science data taken during the encounter will begin streaming to Earth. Navigators will analyze the spacecraft’s trajectory following this downlink to confirm that Cassini is on course to dive into Saturn at the planned time, location and altitude.
How did the Titan flyby set the course for Cassini’s ultimate end? The geometry of the flyby caused Cassini to slow down slightly in its orbit around Saturn. This lowers the altitude of its flight over the planet so that the spacecraft goes too deep into Saturn’s atmosphere to survive, because friction with the atmosphere will cause Cassini to burn up.
Cassini has made hundreds of passes over Titan during its 13-year tour of the Saturn system — including 127 precisely targeted encounters — some at close range and some, like this one, more distant.
Cassini Project Manager Earl Maize at NASA’s Jet Propulsion Laboratory in Pasadena, California, said in a statement:
Cassini has been in a long-term relationship with Titan, with a new rendezvous nearly every month for more than a decade. This final encounter is something of a bittersweet goodbye, but as it has done throughout the mission, Titan’s gravity is once again sending Cassini where we need it to go.
Cassini is running out of fuel. That’s why it’s ending its 13-year tour of the Saturn system with an intentional plunge into the planet. It’s making the plunge – rather than just staying in orbit as a dead spacecraft – because, once the craft is entirely out of fuel, mission engineers can no longer control it. They want to prevent a possible future crash of the spacecraft into one of Saturn’s moons, in particular Enceladus, with its subsurface ocean and signs of hydrothermal activity. Cassini’s plunge into Titan on Friday ensures that Enceladus and the other moons will remain pristine for future exploration.
Bottom line:
Read more: Cassini milestones this week before the final plunge
Artist’s concept of Cassini spacecraft making its final, distant flyby of Saturn’s moon Titan on September 11 Image via NASA/JPL-Caltech.
The Cassini spacecraft at Saturn made a final, distant flyby of the large moon Titan today (September 11, 2017). Mission engineers have been informally referring to this encounter as the goodbye kiss, because, as it occurs, Titan provides Cassini with a gravitational nudge that sends the spacecraft toward its dramatic ending in Saturn’s upper atmosphere this Friday, September 15. NASA said the Titan flyby went as planned today. The spacecraft made its closest approach to Titan at 19:04 UTC (3:04 p.m. EDT; translate to your time zone), at an altitude of 73,974 miles (119,049 km) above the moon’s surface.
Cassini is scheduled to make contact with Earth on September 12, at which time images and other science data taken during the encounter will begin streaming to Earth. Navigators will analyze the spacecraft’s trajectory following this downlink to confirm that Cassini is on course to dive into Saturn at the planned time, location and altitude.
How did the Titan flyby set the course for Cassini’s ultimate end? The geometry of the flyby caused Cassini to slow down slightly in its orbit around Saturn. This lowers the altitude of its flight over the planet so that the spacecraft goes too deep into Saturn’s atmosphere to survive, because friction with the atmosphere will cause Cassini to burn up.
Cassini has made hundreds of passes over Titan during its 13-year tour of the Saturn system — including 127 precisely targeted encounters — some at close range and some, like this one, more distant.
Cassini Project Manager Earl Maize at NASA’s Jet Propulsion Laboratory in Pasadena, California, said in a statement:
Cassini has been in a long-term relationship with Titan, with a new rendezvous nearly every month for more than a decade. This final encounter is something of a bittersweet goodbye, but as it has done throughout the mission, Titan’s gravity is once again sending Cassini where we need it to go.
Cassini is running out of fuel. That’s why it’s ending its 13-year tour of the Saturn system with an intentional plunge into the planet. It’s making the plunge – rather than just staying in orbit as a dead spacecraft – because, once the craft is entirely out of fuel, mission engineers can no longer control it. They want to prevent a possible future crash of the spacecraft into one of Saturn’s moons, in particular Enceladus, with its subsurface ocean and signs of hydrothermal activity. Cassini’s plunge into Titan on Friday ensures that Enceladus and the other moons will remain pristine for future exploration.
Bottom line:
Read more: Cassini milestones this week before the final plunge
Cyclobutadiene has long fascinated organic chemists. It is the 4e analogue of the 6e benzene molecule, yet it could hardly be more different. Despite nearly a century of effort, cyclobutadiene analogues were only first prepared in the 1970s, reflecting its strong antiaromatic character.
Per-trimethylsilylcyclobutadiene 1 offers opportunities to probe the properties of the cyclobutadiene ring as the bulky substituents diminish dimerization and polymerization of the reactive π-bonds. Kostenko and coworkers have now reported on the triplet state of 1.1 They observe three EPR signals of 1 at temperatures above 350 K, and these signals increase in area with increasing temperature. This is strong evidence for the existence of triplet 1 in equilibrium with the lower energy singlet. Using the variable temperature EPR spectra, the singlet triplet gap is 13.9 ± 0.8 kcal mol-1.
The structures of singlet and triplet 1 were optimized at B3LYP-D3/6-311+G(d,p) and shown in Figure 1. The singlet is the expected rectangle, with distinctly different C-C distance around the ring. The triplet is a square, with equivalent C-C distances. Since both the singlet and triplet states are likely to have multireference character, the energies of both states were obtained at RI-MRDDCI2-CASSCF(4,4)/def2-SVP//B3LYPD3/6-311+G(d,p) and give a singlet-triplet gap of 11.8 kcal mol-1, in quite reasonable agreement with experiment.
 singlet |
 triplet |
Figure 1. Optimized geometries of singlet and triplet 1.
1. Kostenko, A.; Tumanskii, B.; Kobayashi, Y.; Nakamoto, M.; Sekiguchi, A.; Apeloig, Y., "Spectroscopic Observation of the Triplet Diradical State of a Cyclobutadiene." Angew. Chem. Int. Ed. 2017, 56, 10183-10187, DOI: 10.1002/anie.201705228.
1: InChI=1S/C16H36Si4/c1-17(2,3)13-14(18(4,5)6)16(20(10,11)12)15(13)19(7,8)9/h1-12H3
InChIkey=AYOHYRSQVCLGKR-UHFFFAOYSA-N
Cyclobutadiene has long fascinated organic chemists. It is the 4e analogue of the 6e benzene molecule, yet it could hardly be more different. Despite nearly a century of effort, cyclobutadiene analogues were only first prepared in the 1970s, reflecting its strong antiaromatic character.
Per-trimethylsilylcyclobutadiene 1 offers opportunities to probe the properties of the cyclobutadiene ring as the bulky substituents diminish dimerization and polymerization of the reactive π-bonds. Kostenko and coworkers have now reported on the triplet state of 1.1 They observe three EPR signals of 1 at temperatures above 350 K, and these signals increase in area with increasing temperature. This is strong evidence for the existence of triplet 1 in equilibrium with the lower energy singlet. Using the variable temperature EPR spectra, the singlet triplet gap is 13.9 ± 0.8 kcal mol-1.
The structures of singlet and triplet 1 were optimized at B3LYP-D3/6-311+G(d,p) and shown in Figure 1. The singlet is the expected rectangle, with distinctly different C-C distance around the ring. The triplet is a square, with equivalent C-C distances. Since both the singlet and triplet states are likely to have multireference character, the energies of both states were obtained at RI-MRDDCI2-CASSCF(4,4)/def2-SVP//B3LYPD3/6-311+G(d,p) and give a singlet-triplet gap of 11.8 kcal mol-1, in quite reasonable agreement with experiment.
|
singlet |
triplet |
Figure 1. Optimized geometries of singlet and triplet 1.
1. Kostenko, A.; Tumanskii, B.; Kobayashi, Y.; Nakamoto, M.; Sekiguchi, A.; Apeloig, Y., "Spectroscopic Observation of the Triplet Diradical State of a Cyclobutadiene." Angew. Chem. Int. Ed. 2017, 56, 10183-10187, DOI: 10.1002/anie.201705228.
1: InChI=1S/C16H36Si4/c1-17(2,3)13-14(18(4,5)6)16(20(10,11)12)15(13)19(7,8)9/h1-12H3
InChIkey=AYOHYRSQVCLGKR-UHFFFAOYSA-N
